Added lightweight generic annotations

Summary: public

Added lightweight genarics annotations to make the code more readable and help the compiler catch bugs.

Fixed some type bugs and improved bridge validation in a few places.

Reviewed By: javache

Differential Revision: D2600189

fb-gh-sync-id: f81e22f2cdc107bf8d0b15deec6d5b83aacc5b56

Examples/UIExplorer/UIExplorer.xcodeproj/project.pbxproj

@@ -51,7 +51,7 @@
 		14D6D7291B2222EF001FB087 /* libReact.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 14AADF041AC3DB95002390C9 /* libReact.a */; };
 		14DC67F41AB71881001358AB /* libRCTPushNotification.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 14DC67F11AB71876001358AB /* libRCTPushNotification.a */; };
 		3578590A1B28D2CF00341EDB /* libRCTLinking.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 357859011B28D2C500341EDB /* libRCTLinking.a */; };
-		3D36915B1BDA8CBB007B22D8 /* uie_thumb_big.png in Resources */ = {isa = PBXBuildFile; fileRef = 3D36915A1BDA8CBB007B22D8 /* uie_thumb_big.png */; settings = {ASSET_TAGS = (); }; };
+		3D36915B1BDA8CBB007B22D8 /* uie_thumb_big.png in Resources */ = {isa = PBXBuildFile; fileRef = 3D36915A1BDA8CBB007B22D8 /* uie_thumb_big.png */; };
 		3DB99D0C1BA0340600302749 /* UIExplorerIntegrationTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 3DB99D0B1BA0340600302749 /* UIExplorerIntegrationTests.m */; };
 		834C36EC1AF8DED70019C93C /* libRCTSettings.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 834C36D21AF8DA610019C93C /* libRCTSettings.a */; };
 		83636F8F1B53F22C009F943E /* RCTUIManagerScenarioTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 83636F8E1B53F22C009F943E /* RCTUIManagerScenarioTests.m */; };
@@ -1082,6 +1082,7 @@
 					"$(inherited)",
 				);
 				GCC_SYMBOLS_PRIVATE_EXTERN = NO;
+				GCC_TREAT_INCOMPATIBLE_POINTER_TYPE_WARNINGS_AS_ERRORS = YES;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_MISSING_NEWLINE = YES;
 				GCC_WARN_ABOUT_MISSING_PROTOTYPES = YES;
@@ -1109,6 +1110,7 @@
 				WARNING_CFLAGS = (
 					"-Wextra",
 					"-Wall",
+					"-Wincompatible-pointer-types",
 				);
 			};
 			name = Debug;
@@ -1139,6 +1141,7 @@
 				ENABLE_NS_ASSERTIONS = NO;
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu99;
+				GCC_TREAT_INCOMPATIBLE_POINTER_TYPE_WARNINGS_AS_ERRORS = YES;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
 				GCC_WARN_ABOUT_MISSING_NEWLINE = YES;
 				GCC_WARN_ABOUT_MISSING_PROTOTYPES = YES;
@@ -1166,6 +1169,7 @@
 				WARNING_CFLAGS = (
 					"-Wextra",
 					"-Wall",
+					"-Wincompatible-pointer-types",
 				);
 			};
 			name = Release;

Libraries/ART/Brushes/ARTLinearGradient.m

@@ -19,7 +19,7 @@
   CGPoint _endPoint;
 }
 
-- (instancetype)initWithArray:(NSArray *)array
+- (instancetype)initWithArray:(NSArray<NSNumber *> *)array
 {
   if ((self = [super initWithArray:array])) {
     if (array.count < 5) {

Libraries/ART/Brushes/ARTPattern.m

@@ -18,7 +18,7 @@
   CGRect _rect;
 }
 
-- (instancetype)initWithArray:(NSArray *)array
+- (instancetype)initWithArray:(NSArray<id /* imagesource + numbers */> *)array
 {
   if ((self = [super initWithArray:array])) {
     if (array.count < 6) {

Libraries/ART/Brushes/ARTRadialGradient.m

@@ -21,7 +21,7 @@
   CGFloat _radiusRatio;
 }
 
-- (instancetype)initWithArray:(NSArray *)array
+- (instancetype)initWithArray:(NSArray<NSNumber *> *)array
 {
   if ((self = [super initWithArray:array])) {
     if (array.count < 7) {

Libraries/ART/Brushes/ARTSolidColor.m

@@ -17,7 +17,7 @@
   CGColorRef _color;
 }
 
-- (instancetype)initWithArray:(NSArray *)array
+- (instancetype)initWithArray:(NSArray<NSNumber *> *)array
 {
   if ((self = [super initWithArray:array])) {
     _color = CGColorRetain([RCTConvert CGColor:array offset:1]);

Libraries/ActionSheetIOS/RCTActionSheetManager.m

@@ -62,7 +62,7 @@ RCT_EXPORT_METHOD(showActionSheetWithOptions:(NSDictionary *)options
   }
 
   NSString *title = [RCTConvert NSString:options[@"title"]];
-  NSArray *buttons = [RCTConvert NSStringArray:options[@"options"]];
+  NSArray<NSString *> *buttons = [RCTConvert NSStringArray:options[@"options"]];
   NSInteger destructiveButtonIndex = options[@"destructiveButtonIndex"] ? [RCTConvert NSInteger:options[@"destructiveButtonIndex"]] : -1;
   NSInteger cancelButtonIndex = options[@"cancelButtonIndex"] ? [RCTConvert NSInteger:options[@"cancelButtonIndex"]] : -1;
 
@@ -151,7 +151,7 @@ RCT_EXPORT_METHOD(showShareActionSheetWithOptions:(NSDictionary *)options
     return;
   }
 
-  NSMutableArray *items = [NSMutableArray array];
+  NSMutableArray<id /* NSString or NSURL */> *items = [NSMutableArray array];
   NSString *message = [RCTConvert NSString:options[@"message"]];
   if (message) {
     [items addObject:message];

Libraries/CameraRoll/RCTCameraRollManager.h

@@ -7,7 +7,17 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  */
 
+#import <AssetsLibrary/AssetsLibrary.h>
+
 #import "RCTBridgeModule.h"
+#import "RCTConvert.h"
+
+@interface RCTConvert (ALAssetGroup)
+
++ (ALAssetsGroupType)ALAssetsGroupType:(id)json;
++ (ALAssetsFilter *)ALAssetsFilter:(id)json;
+
+@end
 
 @interface RCTCameraRollManager : NSObject <RCTBridgeModule>
 

Libraries/CameraRoll/RCTCameraRollManager.m

@@ -9,17 +9,70 @@
 
 #import "RCTCameraRollManager.h"
 
-#import <AssetsLibrary/AssetsLibrary.h>
 #import <CoreLocation/CoreLocation.h>
 #import <Foundation/Foundation.h>
 #import <UIKit/UIKit.h>
 
 #import "RCTAssetsLibraryImageLoader.h"
 #import "RCTBridge.h"
+#import "RCTConvert.h"
 #import "RCTImageLoader.h"
 #import "RCTLog.h"
 #import "RCTUtils.h"
 
+@implementation RCTConvert (ALAssetGroup)
+
+RCT_ENUM_CONVERTER(ALAssetsGroupType, (@{
+
+  // New values
+  @"album": @(ALAssetsGroupAlbum),
+  @"all": @(ALAssetsGroupAll),
+  @"event": @(ALAssetsGroupEvent),
+  @"faces": @(ALAssetsGroupFaces),
+  @"library": @(ALAssetsGroupLibrary),
+  @"photo-stream": @(ALAssetsGroupPhotoStream),
+  @"saved-photos": @(ALAssetsGroupSavedPhotos),
+
+  // Legacy values
+  @"Album": @(ALAssetsGroupAlbum),
+  @"All": @(ALAssetsGroupAll),
+  @"Event": @(ALAssetsGroupEvent),
+  @"Faces": @(ALAssetsGroupFaces),
+  @"Library": @(ALAssetsGroupLibrary),
+  @"PhotoStream": @(ALAssetsGroupPhotoStream),
+  @"SavedPhotos": @(ALAssetsGroupSavedPhotos),
+
+}), ALAssetsGroupSavedPhotos, integerValue)
+
++ (ALAssetsFilter *)ALAssetsFilter:(id)json
+{
+  static NSDictionary *options;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    options = @{
+
+      // New values
+      @"photos": [ALAssetsFilter allPhotos],
+      @"videos": [ALAssetsFilter allVideos],
+      @"all": [ALAssetsFilter allAssets],
+
+      // Legacy values
+      @"Photos": [ALAssetsFilter allPhotos],
+      @"Videos": [ALAssetsFilter allVideos],
+      @"All": [ALAssetsFilter allAssets],
+    };
+  });
+
+  ALAssetsFilter *filter = options[json ?: @"photos"];
+  if (!filter) {
+    RCTLogError(@"Invalid filter option: '%@'. Expected one of 'photos',"
+                "'videos' or 'all'.", json);
+  }
+  return filter ?: [ALAssetsFilter allPhotos];
+}
+
+@end
+
 @implementation RCTCameraRollManager
 
 RCT_EXPORT_MODULE()
@@ -49,7 +102,9 @@ RCT_EXPORT_METHOD(saveImageWithTag:(NSString *)imageTag
   }];
 }
 
-- (void)callCallback:(RCTResponseSenderBlock)callback withAssets:(NSArray *)assets hasNextPage:(BOOL)hasNextPage
+- (void)callCallback:(RCTResponseSenderBlock)callback
+          withAssets:(NSArray<NSDictionary *> *)assets
+         hasNextPage:(BOOL)hasNextPage
 {
   if (!assets.count) {
     callback(@[@{
@@ -72,45 +127,21 @@ RCT_EXPORT_METHOD(getPhotos:(NSDictionary *)params
                   callback:(RCTResponseSenderBlock)callback
                   errorCallback:(RCTResponseErrorBlock)errorCallback)
 {
-  NSUInteger first = [params[@"first"] integerValue];
+  NSUInteger first = [RCTConvert NSInteger:params[@"first"]];
-  NSString *afterCursor = params[@"after"];
+  NSString *afterCursor = [RCTConvert NSString:params[@"after"]];
-  NSString *groupTypesStr = params[@"groupTypes"];
+  NSString *groupName = [RCTConvert NSString:params[@"groupName"]];
-  NSString *groupName = params[@"groupName"];
+  ALAssetsFilter *assetType = [RCTConvert ALAssetsFilter:params[@"assetType"]];
-  NSString *assetType = params[@"assetType"];
+  ALAssetsGroupType groupTypes = [RCTConvert ALAssetsGroupType:params[@"groupTypes"]];
-  ALAssetsGroupType groupTypes;
-
-  if ([groupTypesStr isEqualToString:@"Album"]) {
-    groupTypes = ALAssetsGroupAlbum;
-  } else if ([groupTypesStr isEqualToString:@"All"]) {
-    groupTypes = ALAssetsGroupAll;
-  } else if ([groupTypesStr isEqualToString:@"Event"]) {
-    groupTypes = ALAssetsGroupEvent;
-  } else if ([groupTypesStr isEqualToString:@"Faces"]) {
-    groupTypes = ALAssetsGroupFaces;
-  } else if ([groupTypesStr isEqualToString:@"Library"]) {
-    groupTypes = ALAssetsGroupLibrary;
-  } else if ([groupTypesStr isEqualToString:@"PhotoStream"]) {
-    groupTypes = ALAssetsGroupPhotoStream;
-  } else {
-    groupTypes = ALAssetsGroupSavedPhotos;
-  }
 
   BOOL __block foundAfter = NO;
   BOOL __block hasNextPage = NO;
   BOOL __block calledCallback = NO;
-  NSMutableArray *assets = [NSMutableArray new];
+  NSMutableArray<NSDictionary *> *assets = [NSMutableArray new];
 
   [_bridge.assetsLibrary enumerateGroupsWithTypes:groupTypes usingBlock:^(ALAssetsGroup *group, BOOL *stopGroups) {
     if (group && (groupName == nil || [groupName isEqualToString:[group valueForProperty:ALAssetsGroupPropertyName]])) {
 
-      if (assetType == nil || [assetType isEqualToString:@"Photos"]) {
+      [group setAssetsFilter:assetType];
-        [group setAssetsFilter:ALAssetsFilter.allPhotos];
-      } else if ([assetType isEqualToString:@"Videos"]) {
-        [group setAssetsFilter:ALAssetsFilter.allVideos];
-      } else if ([assetType isEqualToString:@"All"]) {
-        [group setAssetsFilter:ALAssetsFilter.allAssets];
-      }
-
       [group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stopAssets) {
         if (result) {
           NSString *uri = ((NSURL *)[result valueForProperty:ALAssetPropertyAssetURL]).absoluteString;

Libraries/CameraRoll/RCTImagePickerManager.m

@@ -23,9 +23,9 @@
 
 @implementation RCTImagePickerManager
 {
-  NSMutableArray *_pickers;
+  NSMutableArray<UIImagePickerController *> *_pickers;
-  NSMutableArray *_pickerCallbacks;
+  NSMutableArray<RCTResponseSenderBlock> *_pickerCallbacks;
-  NSMutableArray *_pickerCancelCallbacks;
+  NSMutableArray<RCTResponseSenderBlock> *_pickerCancelCallbacks;
 }
 
 RCT_EXPORT_MODULE(ImagePickerIOS);
@@ -42,7 +42,7 @@ RCT_EXPORT_MODULE(ImagePickerIOS);
 
 RCT_EXPORT_METHOD(canRecordVideos:(RCTResponseSenderBlock)callback)
 {
-  NSArray *availableMediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];
+  NSArray<NSString *> *availableMediaTypes = [UIImagePickerController availableMediaTypesForSourceType:UIImagePickerControllerSourceTypeCamera];
   callback(@[@([availableMediaTypes containsObject:(NSString *)kUTTypeMovie])]);
 }
 
@@ -59,7 +59,7 @@ RCT_EXPORT_METHOD(openCameraDialog:(NSDictionary *)config
     cancelCallback(@[@"Camera access is unavailable in an app extension"]);
     return;
   }
-  
+
   UIWindow *keyWindow = RCTSharedApplication().keyWindow;
   UIViewController *rootViewController = keyWindow.rootViewController;
 
@@ -86,7 +86,7 @@ RCT_EXPORT_METHOD(openSelectDialog:(NSDictionary *)config
     cancelCallback(@[@"Image picker is currently unavailable in an app extension"]);
     return;
   }
-  
+
   UIWindow *keyWindow = RCTSharedApplication().keyWindow;
   UIViewController *rootViewController = keyWindow.rootViewController;
 
@@ -94,7 +94,7 @@ RCT_EXPORT_METHOD(openSelectDialog:(NSDictionary *)config
   imagePicker.delegate = self;
   imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
 
-  NSMutableArray *allowedTypes = [NSMutableArray new];
+  NSMutableArray<NSString *> *allowedTypes = [NSMutableArray new];
   if ([config[@"showImages"] boolValue]) {
     [allowedTypes addObject:(NSString *)kUTTypeImage];
   }

Libraries/Geolocation/RCTLocationObserver.m

@@ -100,7 +100,7 @@ static NSDictionary *RCTPositionError(RCTPositionErrorCode code, NSString *msg /
 {
   CLLocationManager *_locationManager;
   NSDictionary *_lastLocationEvent;
-  NSMutableArray *_pendingRequests;
+  NSMutableArray<RCTLocationRequest *> *_pendingRequests;
   BOOL _observingLocation;
   RCTLocationOptions _observerOptions;
 }
@@ -249,7 +249,8 @@ RCT_EXPORT_METHOD(getCurrentPosition:(RCTLocationOptions)options
 
 #pragma mark - CLLocationManagerDelegate
 
-- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
+- (void)locationManager:(CLLocationManager *)manager
+     didUpdateLocations:(NSArray<CLLocation *> *)locations
 {
   // Create event
   CLLocation *location = locations.lastObject;

Libraries/Image/RCTGIFImageDecoder.m

@@ -42,8 +42,8 @@ RCT_EXPORT_MODULE()
   if (imageCount > 1) {
 
     NSTimeInterval duration = 0;
-    NSMutableArray *delays = [NSMutableArray arrayWithCapacity:imageCount];
+    NSMutableArray<NSNumber *> *delays = [NSMutableArray arrayWithCapacity:imageCount];
-    NSMutableArray *images = [NSMutableArray arrayWithCapacity:imageCount];
+    NSMutableArray<id /* CGIMageRef */> *images = [NSMutableArray arrayWithCapacity:imageCount];
     for (size_t i = 0; i < imageCount; i++) {
 
       CGImageRef imageRef = CGImageSourceCreateImageAtIndex(imageSource, i, NULL);
@@ -75,7 +75,7 @@ RCT_EXPORT_MODULE()
     }
     CFRelease(imageSource);
 
-    NSMutableArray *keyTimes = [NSMutableArray arrayWithCapacity:delays.count];
+    NSMutableArray<NSNumber *> *keyTimes = [NSMutableArray arrayWithCapacity:delays.count];
     NSTimeInterval runningDuration = 0;
     for (NSNumber *delayNumber in delays) {
       [keyTimes addObject:@(runningDuration / duration)];

Libraries/Image/RCTImageLoader.m

@@ -35,8 +35,8 @@
 
 @implementation RCTImageLoader
 {
-  NSArray *_loaders;
+  NSArray<id<RCTImageURLLoader>> *_loaders;
-  NSArray *_decoders;
+  NSArray<id<RCTImageDataDecoder>> *_decoders;
   NSURLCache *_cache;
 }
 
@@ -47,14 +47,14 @@ RCT_EXPORT_MODULE()
 - (void)setBridge:(RCTBridge *)bridge
 {
   // Get image loaders and decoders
-  NSMutableArray *loaders = [NSMutableArray array];
+  NSMutableArray<id<RCTImageURLLoader>> *loaders = [NSMutableArray array];
-  NSMutableArray *decoders = [NSMutableArray array];
+  NSMutableArray<id<RCTImageDataDecoder>> *decoders = [NSMutableArray array];
   for (id<RCTBridgeModule> module in bridge.modules.allValues) {
     if ([module conformsToProtocol:@protocol(RCTImageURLLoader)]) {
-      [loaders addObject:module];
+      [loaders addObject:(id<RCTImageURLLoader>)module];
     }
     if ([module conformsToProtocol:@protocol(RCTImageDataDecoder)]) {
-      [decoders addObject:module];
+      [decoders addObject:(id<RCTImageDataDecoder>)module];
     }
   }
 

Libraries/Network/RCTHTTPRequestHandler.m

@@ -47,7 +47,7 @@ RCT_EXPORT_MODULE()
 
 - (BOOL)canHandleRequest:(NSURLRequest *)request
 {
-  static NSSet *schemes = nil;
+  static NSSet<NSString *> *schemes = nil;
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
     // technically, RCTHTTPRequestHandler can handle file:// as well,

Libraries/Network/RCTNetworking.m

@@ -37,7 +37,7 @@ typedef RCTURLRequestCancellationBlock (^RCTHTTPQueryResult)(NSError *error, NSD
 
 @implementation RCTHTTPFormDataHelper
 {
-  NSMutableArray *_parts;
+  NSMutableArray<NSDictionary *> *_parts;
   NSMutableData *_multipartBody;
   RCTHTTPQueryResult _callback;
   NSString *_boundary;
@@ -122,7 +122,7 @@ static NSString *RCTGenerateFormBoundary()
 @implementation RCTNetworking
 {
   NSMutableDictionary *_tasksByRequestID;
-  NSArray *_handlers;
+  NSArray<id<RCTURLRequestHandler>> *_handlers;
 }
 
 @synthesize bridge = _bridge;
@@ -133,10 +133,10 @@ RCT_EXPORT_MODULE()
 - (void)setBridge:(RCTBridge *)bridge
 {
   // get handlers
-  NSMutableArray *handlers = [NSMutableArray array];
+  NSMutableArray<id<RCTURLRequestHandler>> *handlers = [NSMutableArray array];
   for (id<RCTBridgeModule> module in bridge.modules.allValues) {
     if ([module conformsToProtocol:@protocol(RCTURLRequestHandler)]) {
-      [handlers addObject:module];
+      [handlers addObject:(id<RCTURLRequestHandler>)module];
     }
   }
 

Libraries/RCTTest/RCTTestRunner.h

@@ -22,6 +22,8 @@
                 referenceDirectory:@FB_REFERENCE_IMAGE_DIR \
                     moduleProvider:(moduleProvider__)]
 
+@protocol RCTBridgeModule;
+
 @interface RCTTestRunner : NSObject
 
 @property (nonatomic, assign) BOOL recordMode;
@@ -37,7 +39,7 @@
  */
 - (instancetype)initWithApp:(NSString *)app
          referenceDirectory:(NSString *)referenceDirectory
-             moduleProvider:(NSArray *(^)(void))block NS_DESIGNATED_INITIALIZER;
+             moduleProvider:(NSArray<id<RCTBridgeModule>> *(^)(void))block NS_DESIGNATED_INITIALIZER;
 
 /**
  * Simplest runTest function simply mounts the specified JS module with no

Libraries/RCTTest/RCTTestRunner.m

@@ -126,7 +126,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
     RCTSetLogFunction(RCTDefaultLogFunction);
 
-    NSArray *nonLayoutSubviews = [vc.view.subviews filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id subview, NSDictionary *bindings) {
+    NSArray<UIView *> *nonLayoutSubviews = [vc.view.subviews filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(id subview, NSDictionary *bindings) {
       return ![NSStringFromClass([subview class]) isEqualToString:@"_UILayoutGuide"];
     }]];
     RCTAssert(nonLayoutSubviews.count == 0, @"There shouldn't be any other views: %@", nonLayoutSubviews);

Libraries/Text/RCTShadowText.m

@@ -80,7 +80,7 @@ static css_dim_t RCTMeasure(void *context, float width)
   [self dirtyText];
 }
 
-- (NSDictionary *)processUpdatedProperties:(NSMutableSet *)applierBlocks
+- (NSDictionary *)processUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                           parentProperties:(NSDictionary *)parentProperties
 {
   parentProperties = [super processUpdatedProperties:applierBlocks
@@ -99,7 +99,7 @@ static css_dim_t RCTMeasure(void *context, float width)
 }
 
 - (void)applyLayoutNode:(css_node_t *)node
-      viewsWithNewFrame:(NSMutableSet *)viewsWithNewFrame
+      viewsWithNewFrame:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
        absolutePosition:(CGPoint)absolutePosition
 {
   [super applyLayoutNode:node viewsWithNewFrame:viewsWithNewFrame absolutePosition:absolutePosition];

Libraries/Text/RCTText.m

@@ -16,7 +16,7 @@
 @implementation RCTText
 {
   NSTextStorage *_textStorage;
-  NSMutableArray *_reactSubviews;
+  NSMutableArray<UIView *> *_reactSubviews;
   CAShapeLayer *_highlightLayer;
 }
 
@@ -62,7 +62,7 @@
   [_reactSubviews removeObject:subview];
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<UIView *> *)reactSubviews
 {
   return _reactSubviews;
 }

Libraries/Text/RCTTextField.m

@@ -17,7 +17,7 @@
 @implementation RCTTextField
 {
   RCTEventDispatcher *_eventDispatcher;
-  NSMutableArray *_reactSubviews;
+  NSMutableArray<UIView *> *_reactSubviews;
   BOOL _jsRequestingFirstResponder;
   NSInteger _nativeEventCount;
 }
@@ -92,7 +92,7 @@ static void RCTUpdatePlaceholder(RCTTextField *self)
   RCTUpdatePlaceholder(self);
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<UIView *> *)reactSubviews
 {
   // TODO: do we support subviews of textfield in React?
   // In any case, we should have a better approach than manually

Libraries/Text/RCTTextManager.m

@@ -65,7 +65,7 @@ RCT_EXPORT_SHADOW_PROPERTY(allowFontScaling, BOOL)
       continue;
     }
 
-    NSMutableArray *queue = [NSMutableArray arrayWithObject:rootView];
+    NSMutableArray<RCTShadowView *> *queue = [NSMutableArray arrayWithObject:rootView];
     for (NSInteger i = 0; i < queue.count; i++) {
       RCTShadowView *shadowView = queue[i];
       RCTAssert([shadowView isTextDirty], @"Don't process any nodes that don't have dirty text");

Libraries/WebSocket/RCTSRWebSocket.h

@@ -60,11 +60,11 @@ extern NSString *const RCTSRHTTPResponseErrorKey;
 @property (nonatomic, readonly, copy) NSString *protocol;
 
 // Protocols should be an array of strings that turn into Sec-WebSocket-Protocol.
-- (instancetype)initWithURLRequest:(NSURLRequest *)request protocols:(NSArray *)protocols NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithURLRequest:(NSURLRequest *)request protocols:(NSArray<NSString *> *)protocols NS_DESIGNATED_INITIALIZER;
 - (instancetype)initWithURLRequest:(NSURLRequest *)request;
 
 // Some helper constructors.
-- (instancetype)initWithURL:(NSURL *)url protocols:(NSArray *)protocols;
+- (instancetype)initWithURL:(NSURL *)url protocols:(NSArray<NSString *> *)protocols;
 - (instancetype)initWithURL:(NSURL *)url;
 
 // Delegate queue will be dispatch_main_queue by default.

Libraries/WebSocket/RCTSRWebSocket.m

@@ -186,7 +186,7 @@ typedef void (^data_callback)(RCTSRWebSocket *webSocket,  NSData *data);
   dispatch_queue_t _delegateDispatchQueue;
 
   dispatch_queue_t _workQueue;
-  NSMutableArray *_consumers;
+  NSMutableArray<RCTSRIOConsumer *> *_consumers;
 
   NSInputStream *_inputStream;
   NSOutputStream *_outputStream;
@@ -228,12 +228,12 @@ typedef void (^data_callback)(RCTSRWebSocket *webSocket,  NSData *data);
 
   BOOL _isPumping;
 
-  NSMutableSet *_scheduledRunloops;
+  NSMutableSet<NSArray *> *_scheduledRunloops;
 
   // We use this to retain ourselves.
   __strong RCTSRWebSocket *_selfRetain;
 
-  NSArray *_requestedProtocols;
+  NSArray<NSString *> *_requestedProtocols;
   RCTSRIOConsumerPool *_consumerPool;
 }
 
@@ -244,7 +244,7 @@ static __strong NSData *CRLFCRLF;
   CRLFCRLF = [[NSData alloc] initWithBytes:"\r\n\r\n" length:4];
 }
 
-- (instancetype)initWithURLRequest:(NSURLRequest *)request protocols:(NSArray *)protocols;
+- (instancetype)initWithURLRequest:(NSURLRequest *)request protocols:(NSArray<NSString *> *)protocols;
 {
   RCTAssertParam(request);
 
@@ -271,7 +271,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   return [self initWithURL:URL protocols:nil];
 }
 
-- (instancetype)initWithURL:(NSURL *)URL protocols:(NSArray *)protocols;
+- (instancetype)initWithURL:(NSURL *)URL protocols:(NSArray<NSString *> *)protocols;
 {
   NSURLRequest *request = URL ? [NSURLRequest requestWithURL:URL] : nil;
   return [self initWithURLRequest:request protocols:protocols];
@@ -1456,7 +1456,7 @@ static const size_t RCTSRFrameHeaderOverhead = 32;
 @implementation RCTSRIOConsumerPool
 {
   NSUInteger _poolSize;
-  NSMutableArray *_bufferedConsumers;
+  NSMutableArray<RCTSRIOConsumer *> *_bufferedConsumers;
 }
 
 - (instancetype)initWithBufferCapacity:(NSUInteger)poolSize;

React/Base/RCTAssert.m

@@ -59,7 +59,7 @@ void RCTAddAssertFunction(RCTAssertFunction assertFunction)
 static RCTAssertFunction RCTGetLocalAssertFunction()
 {
   NSMutableDictionary *threadDictionary = [NSThread currentThread].threadDictionary;
-  NSArray *functionStack = threadDictionary[RCTAssertFunctionStack];
+  NSArray<RCTAssertFunction> *functionStack = threadDictionary[RCTAssertFunctionStack];
   RCTAssertFunction assertFunction = functionStack.lastObject;
   if (assertFunction) {
     return assertFunction;
@@ -70,7 +70,7 @@ static RCTAssertFunction RCTGetLocalAssertFunction()
 void RCTPerformBlockWithAssertFunction(void (^block)(void), RCTAssertFunction assertFunction)
 {
   NSMutableDictionary *threadDictionary = [NSThread currentThread].threadDictionary;
-  NSMutableArray *functionStack = threadDictionary[RCTAssertFunctionStack];
+  NSMutableArray<RCTAssertFunction> *functionStack = threadDictionary[RCTAssertFunctionStack];
   if (!functionStack) {
     functionStack = [NSMutableArray new];
     threadDictionary[RCTAssertFunctionStack] = functionStack;

React/Base/RCTBatchedBridge.m

@@ -11,6 +11,7 @@
 
 #import "RCTAssert.h"
 #import "RCTBridge.h"
+#import "RCTBridgeMethod.h"
 #import "RCTConvert.h"
 #import "RCTContextExecutor.h"
 #import "RCTFrameUpdate.h"
@@ -18,7 +19,6 @@
 #import "RCTLog.h"
 #import "RCTModuleData.h"
 #import "RCTModuleMap.h"
-#import "RCTBridgeMethod.h"
 #import "RCTPerformanceLogger.h"
 #import "RCTProfile.h"
 #import "RCTRedBox.h"
@@ -43,7 +43,7 @@ typedef NS_ENUM(NSUInteger, RCTBridgeFields) {
   RCTBridgeFieldParamss,
 };
 
-RCT_EXTERN NSArray *RCTGetModuleClasses(void);
+RCT_EXTERN NSArray<Class> *RCTGetModuleClasses(void);
 
 @interface RCTBridge ()
 
@@ -64,11 +64,11 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
   BOOL _valid;
   BOOL _wasBatchActive;
   __weak id<RCTJavaScriptExecutor> _javaScriptExecutor;
-  NSMutableArray *_pendingCalls;
+  NSMutableArray<NSArray *> *_pendingCalls;
-  NSMutableArray *_moduleDataByID;
+  NSMutableArray<RCTModuleData *> *_moduleDataByID;
   RCTModuleMap *_modulesByName;
   CADisplayLink *_jsDisplayLink;
-  NSMutableSet *_frameUpdateObservers;
+  NSMutableSet<RCTModuleData *> *_frameUpdateObservers;
 }
 
 - (instancetype)initWithParentBridge:(RCTBridge *)bridge
@@ -233,7 +233,7 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
   // Register passed-in module instances
   NSMutableDictionary *preregisteredModules = [NSMutableDictionary new];
 
-  NSArray *extraModules = nil;
+  NSArray<id<RCTBridgeModule>> *extraModules = nil;
   if (self.delegate) {
     if ([self.delegate respondsToSelector:@selector(extraModulesForBridge:)]) {
       extraModules = [self.delegate extraModulesForBridge:_parentBridge];
@@ -308,12 +308,11 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
 
 - (NSString *)moduleConfig
 {
-  NSMutableArray *config = [NSMutableArray new];
+  NSMutableArray<NSArray *> *config = [NSMutableArray new];
   for (RCTModuleData *moduleData in _moduleDataByID) {
     [config addObject:moduleData.config];
     if ([moduleData.instance conformsToProtocol:@protocol(RCTFrameUpdateObserver)]) {
       [_frameUpdateObservers addObject:moduleData];
-
       id<RCTFrameUpdateObserver> observer = (id<RCTFrameUpdateObserver>)moduleData.instance;
       __weak typeof(self) weakSelf = self;
       __weak typeof(_javaScriptExecutor) weakJavaScriptExecutor = _javaScriptExecutor;
@@ -417,7 +416,7 @@ RCT_EXTERN NSArray *RCTGetModuleClasses(void);
 
   _loading = NO;
 
-  NSArray *stack = error.userInfo[@"stack"];
+  NSArray<NSDictionary *> *stack = error.userInfo[@"stack"];
   if (stack) {
     [self.redBox showErrorMessage:error.localizedDescription withStack:stack];
   } else {
@@ -559,7 +558,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
  */
 - (void)enqueueJSCall:(NSString *)moduleDotMethod args:(NSArray *)args
 {
-  NSArray *ids = [moduleDotMethod componentsSeparatedByString:@"."];
+  NSArray<NSString *> *ids = [moduleDotMethod componentsSeparatedByString:@"."];
 
   [self _invokeAndProcessModule:@"BatchedBridge"
                          method:@"callFunctionReturnFlushedQueue"
@@ -698,57 +697,45 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
   }
 }
 
-- (void)handleBuffer:(id)buffer
+- (void)handleBuffer:(NSArray<NSArray *> *)buffer
 {
-  NSArray *requestsArray = [RCTConvert NSArray:buffer];
+  NSArray<NSArray *> *requestsArray = [RCTConvert NSArrayArray:buffer];
 
-#if RCT_DEBUG
+  if (RCT_DEBUG && requestsArray.count <= RCTBridgeFieldParamss) {
-
+    RCTLogError(@"Buffer should contain at least %tu sub-arrays. Only found %tu",
-  if (![buffer isKindOfClass:[NSArray class]]) {
+                RCTBridgeFieldParamss + 1, requestsArray.count);
-    RCTLogError(@"Buffer must be an instance of NSArray, got %@", NSStringFromClass([buffer class]));
     return;
   }
 
-  for (NSUInteger fieldIndex = RCTBridgeFieldRequestModuleIDs; fieldIndex <= RCTBridgeFieldParamss; fieldIndex++) {
+  NSArray<NSNumber *> *moduleIDs = requestsArray[RCTBridgeFieldRequestModuleIDs];
-    id field = requestsArray[fieldIndex];
+  NSArray<NSNumber *> *methodIDs = requestsArray[RCTBridgeFieldMethodIDs];
-    if (![field isKindOfClass:[NSArray class]]) {
+  NSArray<NSArray *> *paramsArrays = requestsArray[RCTBridgeFieldParamss];
-      RCTLogError(@"Field at index %zd in buffer must be an instance of NSArray, got %@", fieldIndex, NSStringFromClass([field class]));
-      return;
-    }
-  }
 
-#endif
+  if (RCT_DEBUG && (moduleIDs.count != methodIDs.count || moduleIDs.count != paramsArrays.count)) {
-
+    RCTLogError(@"Invalid data message - all must be length: %zd", moduleIDs.count);
-  NSArray *moduleIDs = requestsArray[RCTBridgeFieldRequestModuleIDs];
-  NSArray *methodIDs = requestsArray[RCTBridgeFieldMethodIDs];
-  NSArray *paramsArrays = requestsArray[RCTBridgeFieldParamss];
-
-  NSUInteger numRequests = moduleIDs.count;
-
-  if (RCT_DEBUG && (numRequests != methodIDs.count || numRequests != paramsArrays.count)) {
-    RCTLogError(@"Invalid data message - all must be length: %zd", numRequests);
     return;
   }
 
   NSMapTable *buckets = [[NSMapTable alloc] initWithKeyOptions:NSPointerFunctionsStrongMemory
                                                   valueOptions:NSPointerFunctionsStrongMemory
                                                       capacity:_moduleDataByID.count];
-  for (NSUInteger i = 0; i < numRequests; i++) {
+
-    RCTModuleData *moduleData = _moduleDataByID[[moduleIDs[i] integerValue]];
+  [moduleIDs enumerateObjectsUsingBlock:^(NSNumber *moduleID, NSUInteger i, __unused BOOL *stop) {
+    RCTModuleData *moduleData = _moduleDataByID[moduleID.integerValue];
     if (RCT_DEBUG) {
       // verify that class has been registered
       (void)_modulesByName[moduleData.name];
     }
-    id queue = [moduleData queue];
+    dispatch_queue_t queue = moduleData.queue;
-    NSMutableOrderedSet *set = [buckets objectForKey:queue];
+    NSMutableOrderedSet<NSNumber *> *set = [buckets objectForKey:queue];
     if (!set) {
       set = [NSMutableOrderedSet new];
       [buckets setObject:set forKey:queue];
     }
     [set addObject:@(i)];
-  }
+  }];
 
-  for (id queue in buckets) {
+  for (dispatch_queue_t queue in buckets) {
     RCTProfileBeginFlowEvent();
 
     dispatch_block_t block = ^{

React/Base/RCTBridge.h

@@ -52,7 +52,7 @@ RCT_EXTERN NSString *const RCTDidCreateNativeModules;
  * For this reason, the block should always return new module instances, and
  * module instances should not be shared between bridges.
  */
-typedef NSArray *(^RCTBridgeModuleProviderBlock)(void);
+typedef NSArray<id<RCTBridgeModule>> *(^RCTBridgeModuleProviderBlock)(void);
 
 /**
  * This function returns the module name for a given class.

React/Base/RCTBridge.m

@@ -39,9 +39,9 @@ NSString *const RCTDidCreateNativeModules = @"RCTDidCreateNativeModules";
 
 @end
 
-static NSMutableArray *RCTModuleClasses;
+static NSMutableArray<Class> *RCTModuleClasses;
-NSArray *RCTGetModuleClasses(void);
+NSArray<Class> *RCTGetModuleClasses(void);
-NSArray *RCTGetModuleClasses(void)
+NSArray<Class> *RCTGetModuleClasses(void)
 {
   return RCTModuleClasses;
 }

React/Base/RCTBridgeDelegate.h

@@ -10,6 +10,7 @@
 typedef void (^RCTSourceLoadBlock)(NSError *error, NSData *source);
 
 @class RCTBridge;
+@protocol RCTBridgeModule;
 
 @protocol RCTBridgeDelegate <NSObject>
 
@@ -17,7 +18,7 @@ typedef void (^RCTSourceLoadBlock)(NSError *error, NSData *source);
 
 @optional
 
-- (NSArray *)extraModulesForBridge:(RCTBridge *)bridge;
+- (NSArray<id<RCTBridgeModule>> *)extraModulesForBridge:(RCTBridge *)bridge;
 - (void)loadSourceForBridge:(RCTBridge *)bridge withBlock:(RCTSourceLoadBlock)loadCallback;
 
 @end

React/Base/RCTBridgeModule.h

@@ -12,6 +12,7 @@
 #import "RCTDefines.h"
 
 @class RCTBridge;
+@protocol RCTBridgeMethod;
 
 /**
  * The type of a block that is capable of sending a response to a bridged
@@ -208,7 +209,8 @@ RCT_EXTERN void RCTRegisterModule(Class); \
  * Like RCT_EXTERN_REMAP_METHOD, but allows setting a custom JavaScript name.
  */
 #define RCT_EXTERN_REMAP_METHOD(js_name, method) \
-  + (NSArray *)RCT_CONCAT(__rct_export__, RCT_CONCAT(js_name, RCT_CONCAT(__LINE__, __COUNTER__))) { \
+  + (NSArray<NSString *> *)RCT_CONCAT(__rct_export__, \
+    RCT_CONCAT(js_name, RCT_CONCAT(__LINE__, __COUNTER__))) { \
     return @[@#js_name, @#method]; \
   }
 
@@ -217,7 +219,7 @@ RCT_EXTERN void RCTRegisterModule(Class); \
  * methods defined using the macros above.  This method is called only once,
  * before registration.
  */
-- (NSArray *)methodsToExport;
+- (NSArray<id<RCTBridgeMethod>> *)methodsToExport;
 
 /**
  * Injects constants into JS. These constants are made accessible via

React/Base/RCTConvert.h

@@ -96,25 +96,28 @@ typedef NSURL RCTFileURL;
    scaleMultiplier:(CGFloat)scaleMultiplier;
 
 typedef NSArray NSArrayArray;
-+ (NSArrayArray *)NSArrayArray:(id)json;
++ (NSArray<NSArray *> *)NSArrayArray:(id)json;
 
 typedef NSArray NSStringArray;
-+ (NSStringArray *)NSStringArray:(id)json;
++ (NSArray<NSString *> *)NSStringArray:(id)json;
+
+typedef NSArray NSStringArrayArray;
++ (NSArray<NSArray<NSString *> *> *)NSStringArrayArray:(id)json;
 
 typedef NSArray NSDictionaryArray;
-+ (NSDictionaryArray *)NSDictionaryArray:(id)json;
++ (NSArray<NSDictionary *> *)NSDictionaryArray:(id)json;
 
 typedef NSArray NSURLArray;
-+ (NSURLArray *)NSURLArray:(id)json;
++ (NSArray<NSURL *> *)NSURLArray:(id)json;
 
 typedef NSArray RCTFileURLArray;
-+ (RCTFileURLArray *)RCTFileURLArray:(id)json;
++ (NSArray<NSURL *> *)RCTFileURLArray:(id)json;
 
 typedef NSArray NSNumberArray;
-+ (NSNumberArray *)NSNumberArray:(id)json;
++ (NSArray<NSNumber *> *)NSNumberArray:(id)json;
 
 typedef NSArray UIColorArray;
-+ (UIColorArray *)UIColorArray:(id)json;
++ (NSArray<UIColor *> *)UIColorArray:(id)json;
 
 typedef NSArray CGColorArray;
 + (CGColorArray *)CGColorArray:(id)json;
@@ -223,7 +226,7 @@ RCT_CUSTOM_CONVERTER(type, type, [RCT_DEBUG ? [self NSNumber:json] : json getter
  * This macro is used for creating converter functions for typed arrays.
  */
 #define RCT_ARRAY_CONVERTER(type)                      \
-+ (NSArray *)type##Array:(id)json                      \
++ (NSArray<type *> *)type##Array:(id)json                      \
 {                                                      \
   return RCTConvertArrayValue(@selector(type:), json); \
 }

React/Base/RCTConvert.m

@@ -711,6 +711,7 @@ RCT_ARRAY_CONVERTER(UIColor)
 
 RCT_JSON_ARRAY_CONVERTER(NSArray)
 RCT_JSON_ARRAY_CONVERTER(NSString)
+RCT_JSON_ARRAY_CONVERTER(NSStringArray)
 RCT_JSON_ARRAY_CONVERTER(NSDictionary)
 RCT_JSON_ARRAY_CONVERTER(NSNumber)
 

React/Base/RCTEventDispatcher.m

@@ -209,7 +209,7 @@ RCT_EXPORT_MODULE()
 
 - (void)dispatchEvent:(id<RCTEvent>)event
 {
-  NSMutableArray *arguments = [NSMutableArray new];
+  NSMutableArray<id /* any JSON value */> *arguments = [NSMutableArray new];
 
   if (event.viewTag) {
     [arguments addObject:event.viewTag];
@@ -221,8 +221,7 @@ RCT_EXPORT_MODULE()
     [arguments addObject:event.body];
   }
 
-  [_bridge enqueueJSCall:[[event class] moduleDotMethod]
+  [_bridge enqueueJSCall:[[event class] moduleDotMethod] args:arguments];
-                    args:arguments];
 }
 
 - (dispatch_queue_t)methodQueue

React/Base/RCTJavaScriptLoader.m

@@ -82,7 +82,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
       NSDictionary *errorDetails = RCTJSONParse(rawText, nil);
       if ([errorDetails isKindOfClass:[NSDictionary class]] &&
           [errorDetails[@"errors"] isKindOfClass:[NSArray class]]) {
-        NSMutableArray *fakeStack = [NSMutableArray new];
+        NSMutableArray<NSDictionary *> *fakeStack = [NSMutableArray new];
         for (NSDictionary *err in errorDetails[@"errors"]) {
           [fakeStack addObject: @{
             @"methodName": err[@"description"] ?: @"",

React/Base/RCTKeyCommands.m

@@ -77,15 +77,15 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
 @interface RCTKeyCommands ()
 
-@property (nonatomic, strong) NSMutableSet *commands;
+@property (nonatomic, strong) NSMutableSet<RCTKeyCommand *> *commands;
 
 @end
 
 @implementation UIResponder (RCTKeyCommands)
 
-- (NSArray *)RCT_keyCommands
+- (NSArray<UIKeyCommand *> *)RCT_keyCommands
 {
-  NSSet *commands = [RCTKeyCommands sharedInstance].commands;
+  NSSet<RCTKeyCommand *> *commands = [RCTKeyCommands sharedInstance].commands;
   return [[commands valueForKeyPath:@"keyCommand"] allObjects];
 }
 

React/Base/RCTLog.m

@@ -120,7 +120,7 @@ void RCTAddLogFunction(RCTLogFunction logFunction)
 static RCTLogFunction RCTGetLocalLogFunction()
 {
   NSMutableDictionary *threadDictionary = [NSThread currentThread].threadDictionary;
-  NSArray *functionStack = threadDictionary[RCTLogFunctionStack];
+  NSArray<RCTLogFunction> *functionStack = threadDictionary[RCTLogFunctionStack];
   RCTLogFunction logFunction = functionStack.lastObject;
   if (logFunction) {
     return logFunction;
@@ -131,7 +131,7 @@ static RCTLogFunction RCTGetLocalLogFunction()
 void RCTPerformBlockWithLogFunction(void (^block)(void), RCTLogFunction logFunction)
 {
   NSMutableDictionary *threadDictionary = [NSThread currentThread].threadDictionary;
-  NSMutableArray *functionStack = threadDictionary[RCTLogFunctionStack];
+  NSMutableArray<RCTLogFunction> *functionStack = threadDictionary[RCTLogFunctionStack];
   if (!functionStack) {
     functionStack = [NSMutableArray new];
     threadDictionary[RCTLogFunctionStack] = functionStack;
@@ -216,8 +216,9 @@ void _RCTLogInternal(
 
     // Log to red box
     if ([UIApplication sharedApplication] && level >= RCTLOG_REDBOX_LEVEL) {
-      NSArray *stackSymbols = [NSThread callStackSymbols];
+      NSArray<NSString *> *stackSymbols = [NSThread callStackSymbols];
-      NSMutableArray *stack = [NSMutableArray arrayWithCapacity:(stackSymbols.count - 1)];
+      NSMutableArray<NSDictionary *> *stack =
+        [NSMutableArray arrayWithCapacity:(stackSymbols.count - 1)];
       [stackSymbols enumerateObjectsUsingBlock:^(NSString *frameSymbols, NSUInteger idx, __unused BOOL *stop) {
         if (idx > 0) { // don't include the current frame
           NSString *address = [[frameSymbols componentsSeparatedByString:@"0x"][1] componentsSeparatedByString:@" "][0];

React/Base/RCTModuleData.h

@@ -11,6 +11,8 @@
 
 #import "RCTJavaScriptExecutor.h"
 
+@protocol RCTBridgeMethod;
+
 @interface RCTModuleData : NSObject
 
 @property (nonatomic, weak, readonly) id<RCTJavaScriptExecutor> javaScriptExecutor;
@@ -19,7 +21,7 @@
 
 @property (nonatomic, strong, readonly) Class moduleClass;
 @property (nonatomic, copy, readonly) NSString *name;
-@property (nonatomic, copy, readonly) NSArray *methods;
+@property (nonatomic, copy, readonly) NSArray<id<RCTBridgeMethod>> *methods;
 @property (nonatomic, copy, readonly) NSArray *config;
 
 @property (nonatomic, strong) dispatch_queue_t queue;

React/Base/RCTModuleData.m

@@ -17,10 +17,11 @@
 @implementation RCTModuleData
 {
   NSDictionary *_constants;
-  NSArray *_methods;
   NSString *_queueName;
 }
 
+@synthesize methods = _methods;
+
 - (instancetype)initWithExecutor:(id<RCTJavaScriptExecutor>)javaScriptExecutor
                         moduleID:(NSNumber *)moduleID
                         instance:(id<RCTBridgeModule>)instance
@@ -46,10 +47,10 @@
 
 RCT_NOT_IMPLEMENTED(- (instancetype)init);
 
-- (NSArray *)methods
+- (NSArray<id<RCTBridgeMethod>> *)methods
 {
   if (!_methods) {
-    NSMutableArray *moduleMethods = [NSMutableArray new];
+    NSMutableArray<id<RCTBridgeMethod>> *moduleMethods = [NSMutableArray new];
 
     if ([_instance respondsToSelector:@selector(methodsToExport)]) {
       [moduleMethods addObjectsFromArray:[_instance methodsToExport]];
@@ -63,11 +64,12 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init);
       SEL selector = method_getName(method);
       if ([NSStringFromSelector(selector) hasPrefix:@"__rct_export__"]) {
         IMP imp = method_getImplementation(method);
-        NSArray *entries = ((NSArray *(*)(id, SEL))imp)(_moduleClass, selector);
+        NSArray<NSString *> *entries =
+          ((NSArray<NSString *> *(*)(id, SEL))imp)(_moduleClass, selector);
         id<RCTBridgeMethod> moduleMethod =
-        [[RCTModuleMethod alloc] initWithObjCMethodName:entries[1]
+          [[RCTModuleMethod alloc] initWithObjCMethodName:entries[1]
-                                           JSMethodName:entries[0]
+                                             JSMethodName:entries[0]
-                                            moduleClass:_moduleClass];
+                                              moduleClass:_moduleClass];
 
         [moduleMethods addObject:moduleMethod];
       }
@@ -86,8 +88,8 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init);
     return (id)kCFNull; // Nothing to export
   }
 
-  NSMutableArray *methods = self.methods.count ? [NSMutableArray new] : nil;
+  NSMutableArray<NSString *> *methods = self.methods.count ? [NSMutableArray new] : nil;
-  NSMutableArray *asyncMethods = nil;
+  NSMutableArray<NSNumber *> *asyncMethods = nil;
   for (id<RCTBridgeMethod> method in self.methods) {
     if (method.functionType == RCTFunctionTypePromise) {
       if (!asyncMethods) {

React/Base/RCTModuleMap.m

@@ -69,7 +69,7 @@ extern BOOL RCTBridgeModuleClassIsRegistered(Class cls);
   return [_modulesByName keyEnumerator];
 }
 
-- (NSArray *)allValues
+- (NSArray<id<RCTBridgeModule>> *)allValues
 {
   // don't perform validation in this case because we only want to error when
   // an invalid module is specifically requested

React/Base/RCTModuleMethod.m

@@ -47,7 +47,7 @@ typedef BOOL (^RCTArgumentBlock)(RCTBridge *, NSUInteger, id);
 {
   Class _moduleClass;
   NSInvocation *_invocation;
-  NSArray *_argumentBlocks;
+  NSArray<RCTArgumentBlock> *_argumentBlocks;
   NSString *_objCMethodName;
   SEL _selector;
   NSDictionary *_profileArgs;
@@ -66,8 +66,8 @@ static void RCTLogArgumentError(RCTModuleMethod *method, NSUInteger index,
 
 RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
-void RCTParseObjCMethodName(NSString **, NSArray **);
+void RCTParseObjCMethodName(NSString **, NSArray<RCTMethodArgument *> **);
-void RCTParseObjCMethodName(NSString **objCMethodName, NSArray **arguments)
+void RCTParseObjCMethodName(NSString **objCMethodName, NSArray<RCTMethodArgument *> **arguments)
 {
   static NSRegularExpression *typeNameRegex;
   static dispatch_once_t onceToken;
@@ -148,7 +148,7 @@ void RCTParseObjCMethodName(NSString **objCMethodName, NSArray **arguments)
 
 - (void)processMethodSignature
 {
-  NSArray *arguments;
+  NSArray<RCTMethodArgument *> *arguments;
   NSString *objCMethodName = _objCMethodName;
   RCTParseObjCMethodName(&objCMethodName, &arguments);
 
@@ -164,7 +164,8 @@ void RCTParseObjCMethodName(NSString **objCMethodName, NSArray **arguments)
 
   // Process arguments
   NSUInteger numberOfArguments = methodSignature.numberOfArguments;
-  NSMutableArray *argumentBlocks = [[NSMutableArray alloc] initWithCapacity:numberOfArguments - 2];
+  NSMutableArray<RCTArgumentBlock> *argumentBlocks =
+    [[NSMutableArray alloc] initWithCapacity:numberOfArguments - 2];
 
 #define RCT_ARG_BLOCK(_logic) \
 [argumentBlocks addObject:^(__unused RCTBridge *bridge, NSUInteger index, id json) { \

React/Base/RCTPerformanceLogger.h

@@ -25,5 +25,5 @@ typedef NS_ENUM(NSUInteger, RCTPLTag) {
 void RCTPerformanceLoggerStart(RCTPLTag tag);
 void RCTPerformanceLoggerEnd(RCTPLTag tag);
 void RCTPerformanceLoggerSet(RCTPLTag tag, int64_t value);
-NSArray *RCTPerformanceLoggerOutput(void);
+NSArray<NSNumber *> *RCTPerformanceLoggerOutput(void);
 NSArray *RCTPerformanceLoggerLabels(void);

React/Base/RCTPerformanceLogger.m

@@ -36,7 +36,7 @@ void RCTPerformanceLoggerSet(RCTPLTag tag, int64_t value)
   RCTPLData[tag][1] = value;
 }
 
-NSArray *RCTPerformanceLoggerOutput(void)
+NSArray<NSNumber *> *RCTPerformanceLoggerOutput(void)
 {
   return @[
     @(RCTPLData[RCTPLScriptDownload][0]),

React/Base/RCTSparseArray.h

@@ -27,7 +27,7 @@
 - (id)objectForKeyedSubscript:(NSNumber *)key;
 
 @property (readonly, nonatomic) NSUInteger count;
-@property (readonly, nonatomic, copy) NSArray *allIndexes;
+@property (readonly, nonatomic, copy) NSArray<NSNumber *> *allIndexes;
 @property (readonly, nonatomic, copy) NSArray *allObjects;
 
 - (void)enumerateObjectsUsingBlock:(void (^)(id obj, NSNumber *idx, BOOL *stop))block;

React/Base/RCTSparseArray.m

@@ -79,7 +79,7 @@
   return _storage.count;
 }
 
-- (NSArray *)allIndexes
+- (NSArray<NSNumber *> *)allIndexes
 {
   return _storage.allKeys;
 }

React/Base/RCTTouchHandler.m

@@ -31,9 +31,9 @@
    * These must be kept track of because `UIKit` destroys the touch targets
    * if touches are canceled, and we have no other way to recover this info.
    */
-  NSMutableOrderedSet *_nativeTouches;
+  NSMutableOrderedSet<UITouch *> *_nativeTouches;
-  NSMutableArray *_reactTouches;
+  NSMutableArray<NSMutableDictionary *> *_reactTouches;
-  NSMutableArray *_touchViews;
+  NSMutableArray<UIView *> *_touchViews;
 
   BOOL _dispatchedInitialTouches;
   BOOL _recordingInteractionTiming;
@@ -71,7 +71,7 @@ typedef NS_ENUM(NSInteger, RCTTouchEventType) {
 
 #pragma mark - Bookkeeping for touch indices
 
-- (void)_recordNewTouches:(NSSet *)touches
+- (void)_recordNewTouches:(NSSet<UITouch *> *)touches
 {
   for (UITouch *touch in touches) {
 
@@ -121,7 +121,7 @@ typedef NS_ENUM(NSInteger, RCTTouchEventType) {
   }
 }
 
-- (void)_recordRemovedTouches:(NSSet *)touches
+- (void)_recordRemovedTouches:(NSSet<UITouch *> *)touches
 {
   for (UITouch *touch in touches) {
     NSUInteger index = [_nativeTouches indexOfObject:touch];
@@ -163,12 +163,12 @@ typedef NS_ENUM(NSInteger, RCTTouchEventType) {
  * (start/end/move/cancel) and the indices that represent "changed" `Touch`es
  * from that array.
  */
-- (void)_updateAndDispatchTouches:(NSSet *)touches
+- (void)_updateAndDispatchTouches:(NSSet<UITouch *> *)touches
                         eventName:(NSString *)eventName
                   originatingTime:(__unused CFTimeInterval)originatingTime
 {
   // Update touches
-  NSMutableArray *changedIndexes = [NSMutableArray new];
+  NSMutableArray<NSNumber *> *changedIndexes = [NSMutableArray new];
   for (UITouch *touch in touches) {
     NSInteger index = [_nativeTouches indexOfObject:touch];
     if (index == NSNotFound) {
@@ -185,7 +185,8 @@ typedef NS_ENUM(NSInteger, RCTTouchEventType) {
 
   // Deep copy the touches because they will be accessed from another thread
   // TODO: would it be safer to do this in the bridge or executor, rather than trusting caller?
-  NSMutableArray *reactTouches = [[NSMutableArray alloc] initWithCapacity:_reactTouches.count];
+  NSMutableArray<NSDictionary *> *reactTouches =
+    [[NSMutableArray alloc] initWithCapacity:_reactTouches.count];
   for (NSDictionary *touch in _reactTouches) {
     [reactTouches addObject:[touch copy]];
   }
@@ -197,7 +198,7 @@ typedef NS_ENUM(NSInteger, RCTTouchEventType) {
 
 #pragma mark - Gesture Recognizer Delegate Callbacks
 
-static BOOL RCTAllTouchesAreCancelledOrEnded(NSSet *touches)
+static BOOL RCTAllTouchesAreCancelledOrEnded(NSSet<UITouch *> *touches)
 {
   for (UITouch *touch in touches) {
     if (touch.phase == UITouchPhaseBegan ||
@@ -209,7 +210,7 @@ static BOOL RCTAllTouchesAreCancelledOrEnded(NSSet *touches)
   return YES;
 }
 
-static BOOL RCTAnyTouchesChanged(NSSet *touches)
+static BOOL RCTAnyTouchesChanged(NSSet<UITouch *> *touches)
 {
   for (UITouch *touch in touches) {
     if (touch.phase == UITouchPhaseBegan ||
@@ -238,7 +239,7 @@ static BOOL RCTAnyTouchesChanged(NSSet *touches)
   // dispatch the updates from the raw touch methods below.
 }
 
-- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
+- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
   [super touchesBegan:touches withEvent:event];
 
@@ -253,7 +254,7 @@ static BOOL RCTAnyTouchesChanged(NSSet *touches)
   }
 }
 
-- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
+- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
   [super touchesMoved:touches withEvent:event];
 
@@ -263,7 +264,7 @@ static BOOL RCTAnyTouchesChanged(NSSet *touches)
   }
 }
 
-- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
+- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
   [super touchesEnded:touches withEvent:event];
 
@@ -279,7 +280,7 @@ static BOOL RCTAnyTouchesChanged(NSSet *touches)
   [self _recordRemovedTouches:touches];
 }
 
-- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
+- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
   [super touchesCancelled:touches withEvent:event];
 

React/Base/RCTUtils.h

@@ -60,7 +60,11 @@ RCT_EXTERN UIApplication *RCTSharedApplication(void);
 
 // Return a UIAlertView initialized with the given values
 // or nil if running in an app extension
-RCT_EXTERN UIAlertView *RCTAlertView(NSString *title, NSString *message, id delegate, NSString *cancelButtonTitle, NSArray *otherButtonTitles);
+RCT_EXTERN UIAlertView *RCTAlertView(NSString *title,
+                                     NSString *message,
+                                     id delegate,
+                                     NSString *cancelButtonTitle,
+                                     NSArray<NSString *> *otherButtonTitles);
 
 // Return YES if image has an alpha component
 RCT_EXTERN BOOL RCTImageHasAlpha(CGImageRef image);

React/Base/RCTUtils.m

@@ -24,7 +24,7 @@
 NSString *RCTJSONStringify(id jsonObject, NSError **error)
 {
   static SEL JSONKitSelector = NULL;
-  static NSSet *collectionTypes;
+  static NSSet<Class> *collectionTypes;
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
     SEL selector = NSSelectorFromString(@"JSONStringWithOptions:error:");
@@ -121,7 +121,7 @@ id RCTJSONParseMutable(NSString *jsonString, NSError **error)
 id RCTJSONClean(id object)
 {
   static dispatch_once_t onceToken;
-  static NSSet *validLeafTypes;
+  static NSSet<Class> *validLeafTypes;
   dispatch_once(&onceToken, ^{
     validLeafTypes = [[NSSet alloc] initWithArray:@[
       [NSString class],
@@ -301,7 +301,7 @@ NSDictionary *RCTMakeError(NSString *message, id toStringify, NSDictionary *extr
 
 NSDictionary *RCTMakeAndLogError(NSString *message, id toStringify, NSDictionary *extraData)
 {
-  id error = RCTMakeError(message, toStringify, extraData);
+  NSDictionary *error = RCTMakeError(message, toStringify, extraData);
   RCTLogError(@"\nError: %@", error);
   return error;
 }
@@ -310,9 +310,9 @@ NSDictionary *RCTMakeAndLogError(NSString *message, id toStringify, NSDictionary
 NSDictionary *RCTJSErrorFromNSError(NSError *error)
 {
   NSString *errorMessage;
-  NSArray *stackTrace = [NSThread callStackSymbols];
+  NSArray<NSString *> *stackTrace = [NSThread callStackSymbols];
   NSMutableDictionary *errorInfo =
-  [NSMutableDictionary dictionaryWithObject:stackTrace forKey:@"nativeStackIOS"];
+    [NSMutableDictionary dictionaryWithObject:stackTrace forKey:@"nativeStackIOS"];
 
   if (error) {
     errorMessage = error.localizedDescription ?: @"Unknown error from a native module";
@@ -351,7 +351,11 @@ id RCTSharedApplication(void)
   return [[UIApplication class] performSelector:@selector(sharedApplication)];
 }
 
-id RCTAlertView(NSString *title, NSString *message, id delegate, NSString *cancelButtonTitle, NSArray *otherButtonTitles)
+id RCTAlertView(NSString *title,
+                NSString *message,
+                id delegate,
+                NSString *cancelButtonTitle,
+                NSArray<NSString *> *otherButtonTitles)
 {
   if (RCTRunningInAppExtension()) {
     RCTLogError(@"RCTAlertView is unavailable when running in an app extension");
@@ -366,8 +370,7 @@ id RCTAlertView(NSString *title, NSString *message, id delegate, NSString *cance
     [alertView addButtonWithTitle:cancelButtonTitle];
     alertView.cancelButtonIndex = 0;
   }
-  for (NSString *buttonTitle in otherButtonTitles)
+  for (NSString *buttonTitle in otherButtonTitles) {
-  {
     [alertView addButtonWithTitle:buttonTitle];
   }
   return alertView;

React/Executors/RCTContextExecutor.m

@@ -93,7 +93,7 @@ RCT_NOT_IMPLEMENTED(-(instancetype)init)
 // Private bridge interface to allow middle-batch calls
 @interface RCTBridge (RCTContextExecutor)
 
-- (void)handleBuffer:(NSArray *)buffer batchEnded:(BOOL)hasEnded;
+- (void)handleBuffer:(NSArray<NSArray *> *)buffer batchEnded:(BOOL)hasEnded;
 
 @end
 
@@ -345,7 +345,7 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
     [strongSelf _addNativeHook:RCTNoop withName:"noop"];
 
     __weak RCTBridge *bridge = strongSelf->_bridge;
-    strongSelf->_context.context[@"nativeFlushQueueImmediate"] = ^(NSArray *calls){
+    strongSelf->_context.context[@"nativeFlushQueueImmediate"] = ^(NSArray<NSArray *> *calls){
       if (!weakSelf.valid || !calls) {
         return;
       }

React/Modules/RCTAlertManager.m

@@ -10,6 +10,7 @@
 #import "RCTAlertManager.h"
 
 #import "RCTAssert.h"
+#import "RCTConvert.h"
 #import "RCTLog.h"
 #import "RCTUtils.h"
 
@@ -19,10 +20,10 @@
 
 @implementation RCTAlertManager
 {
-  NSMutableArray *_alerts;
+  NSMutableArray<UIAlertView *> *_alerts;
-  NSMutableArray *_alertControllers;
+  NSMutableArray<UIAlertController *> *_alertControllers;
-  NSMutableArray *_alertCallbacks;
+  NSMutableArray<RCTResponseSenderBlock> *_alertCallbacks;
-  NSMutableArray *_alertButtonKeys;
+  NSMutableArray<NSArray<NSString *> *> *_alertButtonKeys;
 }
 
 RCT_EXPORT_MODULE()
@@ -70,10 +71,10 @@ RCT_EXPORT_MODULE()
 RCT_EXPORT_METHOD(alertWithArgs:(NSDictionary *)args
                   callback:(RCTResponseSenderBlock)callback)
 {
-  NSString *title = args[@"title"];
+  NSString *title = [RCTConvert NSString:args[@"title"]];
-  NSString *message = args[@"message"];
+  NSString *message = [RCTConvert NSString:args[@"message"]];
-  NSString *type = args[@"type"];
+  NSString *type = [RCTConvert NSString:args[@"type"]];
-  NSArray *buttons = args[@"buttons"];
+  NSDictionaryArray *buttons = [RCTConvert NSDictionaryArray:args[@"buttons"]];
   BOOL allowsTextInput = [type isEqual:@"plain-text"];
 
   if (!title && !message) {
@@ -95,9 +96,11 @@ RCT_EXPORT_METHOD(alertWithArgs:(NSDictionary *)args
   }
 
 #if __IPHONE_OS_VERSION_MIN_REQUIRED < __IPHONE_8_0
+
   if ([UIAlertController class] == nil) {
+
     UIAlertView *alertView = RCTAlertView(title, nil, self, nil, nil);
-    NSMutableArray *buttonKeys = [[NSMutableArray alloc] initWithCapacity:buttons.count];
+    NSMutableArray<NSString *> *buttonKeys = [[NSMutableArray alloc] initWithCapacity:buttons.count];
 
     if (allowsTextInput) {
       alertView.alertViewStyle = UIAlertViewStylePlainTextInput;
@@ -126,8 +129,11 @@ RCT_EXPORT_METHOD(alertWithArgs:(NSDictionary *)args
     [_alertButtonKeys addObject:buttonKeys];
 
     [alertView show];
+
   } else
+
 #endif
+
   {
     UIAlertController *alertController =
     [UIAlertController alertControllerWithTitle:title
@@ -152,7 +158,7 @@ RCT_EXPORT_METHOD(alertWithArgs:(NSDictionary *)args
       UITextField *textField = allowsTextInput ? alertController.textFields.firstObject : nil;
       [alertController addAction:[UIAlertAction actionWithTitle:buttonTitle
                                                           style:buttonStyle
-                                                        handler:^(UIAlertAction *action) {
+                                                        handler:^(__unused UIAlertAction *action) {
         if (callback) {
           if (allowsTextInput) {
             callback(@[buttonKey, textField.text]);
@@ -175,17 +181,14 @@ RCT_EXPORT_METHOD(alertWithArgs:(NSDictionary *)args
   RCTAssert(index != NSNotFound, @"Dismissed alert was not recognised");
 
   RCTResponseSenderBlock callback = _alertCallbacks[index];
-  NSArray *buttonKeys = _alertButtonKeys[index];
+  NSArray<NSString *> *buttonKeys = _alertButtonKeys[index];
-  NSArray *args;
 
   if (alertView.alertViewStyle == UIAlertViewStylePlainTextInput) {
-    args = @[buttonKeys[buttonIndex], [alertView textFieldAtIndex:0].text];
+    callback(@[buttonKeys[buttonIndex], [alertView textFieldAtIndex:0].text]);
   } else {
-    args = @[buttonKeys[buttonIndex]];
+    callback(@[buttonKeys[buttonIndex]]);
   }
 
-  callback(args);
-
   [_alerts removeObjectAtIndex:index];
   [_alertCallbacks removeObjectAtIndex:index];
   [_alertButtonKeys removeObjectAtIndex:index];

React/Modules/RCTAsyncLocalStorage.h

@@ -27,11 +27,8 @@
 
 @property (nonatomic, readonly, getter=isValid) BOOL valid;
 
-- (void)multiGet:(NSArray *)keys callback:(RCTResponseSenderBlock)callback;
+// Clear the RCTAsyncLocalStorage data from native code
-- (void)multiSet:(NSArray *)kvPairs callback:(RCTResponseSenderBlock)callback;
+- (void)clearAllData;
-- (void)multiRemove:(NSArray *)keys callback:(RCTResponseSenderBlock)callback;
-- (void)clear:(RCTResponseSenderBlock)callback;
-- (void)getAllKeys:(RCTResponseSenderBlock)callback;
 
 // For clearing data when the bridge may not exist, e.g. when logging out.
 + (void)clearAllData;

React/Modules/RCTAsyncLocalStorage.m

@@ -14,6 +14,7 @@
 #import <CommonCrypto/CommonCryptor.h>
 #import <CommonCrypto/CommonDigest.h>
 
+#import "RCTConvert.h"
 #import "RCTLog.h"
 #import "RCTUtils.h"
 
@@ -23,7 +24,7 @@ static const NSUInteger RCTInlineValueThreshold = 100;
 
 #pragma mark - Static helper functions
 
-static id RCTErrorForKey(NSString *key)
+static NSDictionary *RCTErrorForKey(NSString *key)
 {
   if (![key isKindOfClass:[NSString class]]) {
     return RCTMakeAndLogError(@"Invalid key - must be a string.  Key: ", key, @{@"key": key});
@@ -34,7 +35,7 @@ static id RCTErrorForKey(NSString *key)
   }
 }
 
-static void RCTAppendError(id error, NSMutableArray **errors)
+static void RCTAppendError(NSDictionary *error, NSMutableArray<NSDictionary *> **errors)
 {
   if (error && errors) {
     if (!*errors) {
@@ -44,7 +45,7 @@ static void RCTAppendError(id error, NSMutableArray **errors)
   }
 }
 
-static id RCTReadFile(NSString *filePath, NSString *key, NSDictionary **errorOut)
+static NSString *RCTReadFile(NSString *filePath, NSString *key, NSDictionary **errorOut)
 {
   if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
     NSError *error;
@@ -148,6 +149,14 @@ RCT_EXPORT_MODULE()
   return RCTGetMethodQueue();
 }
 
+- (void)clearAllData
+{
+  dispatch_async(RCTGetMethodQueue(), ^{
+    _manifest = [NSMutableDictionary new];
+    RCTDeleteStorageDirectory();
+  });
+}
+
 + (void)clearAllData
 {
   dispatch_async(RCTGetMethodQueue(), ^{
@@ -181,7 +190,7 @@ RCT_EXPORT_MODULE()
   return [RCTGetStorageDirectory() stringByAppendingPathComponent:safeFileName];
 }
 
-- (id)_ensureSetup
+- (NSDictionary *)_ensureSetup
 {
   RCTAssertThread(RCTGetMethodQueue(), @"Must be executed on storage thread");
 
@@ -199,7 +208,7 @@ RCT_EXPORT_MODULE()
   if (!_haveSetup) {
     NSDictionary *errorOut;
     NSString *serialized = RCTReadFile(RCTGetManifestFilePath(), nil, &errorOut);
-    _manifest = serialized ? [RCTJSONParse(serialized, &error) mutableCopy] : [NSMutableDictionary new];
+    _manifest = serialized ? RCTJSONParseMutable(serialized, &error) : [NSMutableDictionary new];
     if (error) {
       RCTLogWarn(@"Failed to parse manifest - creating new one.\n\n%@", error);
       _manifest = [NSMutableDictionary new];
@@ -209,12 +218,12 @@ RCT_EXPORT_MODULE()
   return nil;
 }
 
-- (id)_writeManifest:(NSMutableArray **)errors
+- (NSDictionary *)_writeManifest:(NSMutableArray<NSDictionary *> **)errors
 {
   NSError *error;
   NSString *serialized = RCTJSONStringify(_manifest, &error);
   [serialized writeToFile:RCTGetManifestFilePath() atomically:YES encoding:NSUTF8StringEncoding error:&error];
-  id errorOut;
+  NSDictionary *errorOut;
   if (error) {
     errorOut = RCTMakeError(@"Failed to write manifest file.", error, nil);
     RCTAppendError(errorOut, errors);
@@ -222,20 +231,21 @@ RCT_EXPORT_MODULE()
   return errorOut;
 }
 
-- (id)_appendItemForKey:(NSString *)key toArray:(NSMutableArray *)result
+- (NSDictionary *)_appendItemForKey:(NSString *)key
+                            toArray:(NSMutableArray<NSArray<NSString *> *> *)result
 {
-  id errorOut = RCTErrorForKey(key);
+  NSDictionary *errorOut = RCTErrorForKey(key);
   if (errorOut) {
     return errorOut;
   }
-  id value = [self _getValueForKey:key errorOut:&errorOut];
+  NSString *value = [self _getValueForKey:key errorOut:&errorOut];
   [result addObject:@[key, RCTNullIfNil(value)]]; // Insert null if missing or failure.
   return errorOut;
 }
 
 - (NSString *)_getValueForKey:(NSString *)key errorOut:(NSDictionary **)errorOut
 {
-  id value = _manifest[key]; // nil means missing, null means there is a data file, anything else is an inline value.
+  id value = _manifest[key]; // nil means missing, null means there is a data file, else: NSString
   if (value == (id)kCFNull) {
     NSString *filePath = [self _filePathForKey:key];
     value = RCTReadFile(filePath, key, errorOut);
@@ -243,16 +253,13 @@ RCT_EXPORT_MODULE()
   return value;
 }
 
-- (id)_writeEntry:(NSArray *)entry
+- (NSDictionary *)_writeEntry:(NSArray<NSString *> *)entry
 {
-  if (![entry isKindOfClass:[NSArray class]] || entry.count != 2) {
+  if (entry.count != 2) {
     return RCTMakeAndLogError(@"Entries must be arrays of the form [key: string, value: string], got: ", entry, nil);
   }
-  if (![entry[1] isKindOfClass:[NSString class]]) {
-    return RCTMakeAndLogError(@"Values must be strings, got: ", entry[1], @{@"key": entry[0]});
-  }
   NSString *key = entry[0];
-  id errorOut = RCTErrorForKey(key);
+  NSDictionary *errorOut = RCTErrorForKey(key);
   if (errorOut) {
     return errorOut;
   }
@@ -278,66 +285,63 @@ RCT_EXPORT_MODULE()
 
 #pragma mark - Exported JS Functions
 
-RCT_EXPORT_METHOD(multiGet:(NSArray *)keys
+RCT_EXPORT_METHOD(multiGet:(NSStringArray *)keys
                   callback:(RCTResponseSenderBlock)callback)
 {
-  if (!callback) {
+  NSDictionary *errorOut = [self _ensureSetup];
-    RCTLogError(@"Called getItem without a callback.");
-    return;
-  }
-
-  id errorOut = [self _ensureSetup];
   if (errorOut) {
     callback(@[@[errorOut], (id)kCFNull]);
     return;
   }
-  NSMutableArray *errors;
+  NSMutableArray<NSDictionary *> *errors;
-  NSMutableArray *result = [[NSMutableArray alloc] initWithCapacity:keys.count];
+  NSMutableArray<NSArray<NSString *> *> *result = [[NSMutableArray alloc] initWithCapacity:keys.count];
   for (NSString *key in keys) {
-    id keyError = [self _appendItemForKey:key toArray:result];
+    NSDictionary *keyError = [self _appendItemForKey:key toArray:result];
     RCTAppendError(keyError, &errors);
   }
   callback(@[RCTNullIfNil(errors), result]);
 }
 
-RCT_EXPORT_METHOD(multiSet:(NSArray *)kvPairs
+RCT_EXPORT_METHOD(multiSet:(NSStringArrayArray *)kvPairs
                   callback:(RCTResponseSenderBlock)callback)
 {
-  id errorOut = [self _ensureSetup];
+  NSDictionary *errorOut = [self _ensureSetup];
   if (errorOut) {
     callback(@[@[errorOut]]);
     return;
   }
-  NSMutableArray *errors;
+  NSMutableArray<NSDictionary *> *errors;
-  for (NSArray *entry in kvPairs) {
+  for (NSArray<NSString *> *entry in kvPairs) {
-    id keyError = [self _writeEntry:entry];
+    NSDictionary *keyError = [self _writeEntry:entry];
     RCTAppendError(keyError, &errors);
   }
   [self _writeManifest:&errors];
-  if (callback) {
+  callback(@[RCTNullIfNil(errors)]);
-    callback(@[RCTNullIfNil(errors)]);
-  }
 }
 
-RCT_EXPORT_METHOD(multiMerge:(NSArray *)kvPairs
+RCT_EXPORT_METHOD(multiMerge:(NSStringArrayArray *)kvPairs
-                  callback:(RCTResponseSenderBlock)callback)
+                    callback:(RCTResponseSenderBlock)callback)
 {
-  id errorOut = [self _ensureSetup];
+  NSDictionary *errorOut = [self _ensureSetup];
   if (errorOut) {
     callback(@[@[errorOut]]);
     return;
   }
-  NSMutableArray *errors;
+  NSMutableArray<NSDictionary *> *errors;
-  for (__strong NSArray *entry in kvPairs) {
+  for (__strong NSArray<NSString *> *entry in kvPairs) {
-    id keyError;
+    NSDictionary *keyError;
     NSString *value = [self _getValueForKey:entry[0] errorOut:&keyError];
     if (keyError) {
       RCTAppendError(keyError, &errors);
     } else {
       if (value) {
-        NSMutableDictionary *mergedVal = [RCTJSONParseMutable(value, &keyError) mutableCopy];
+        NSError *jsonError;
-        RCTMergeRecursive(mergedVal, RCTJSONParse(entry[1], &keyError));
+        NSMutableDictionary *mergedVal = RCTJSONParseMutable(value, &jsonError);
-        entry = @[entry[0], RCTJSONStringify(mergedVal, &keyError)];
+        RCTMergeRecursive(mergedVal, RCTJSONParse(entry[1], &jsonError));
+        entry = @[entry[0], RCTNullIfNil(RCTJSONStringify(mergedVal, NULL))];
+        if (jsonError) {
+          keyError = RCTJSErrorFromNSError(jsonError);
+        }
       }
       if (!keyError) {
         keyError = [self _writeEntry:entry];
@@ -346,22 +350,20 @@ RCT_EXPORT_METHOD(multiMerge:(NSArray *)kvPairs
     }
   }
   [self _writeManifest:&errors];
-  if (callback) {
+  callback(@[RCTNullIfNil(errors)]);
-    callback(@[RCTNullIfNil(errors)]);
-  }
 }
 
-RCT_EXPORT_METHOD(multiRemove:(NSArray *)keys
+RCT_EXPORT_METHOD(multiRemove:(NSStringArray *)keys
                   callback:(RCTResponseSenderBlock)callback)
 {
-  id errorOut = [self _ensureSetup];
+  NSDictionary *errorOut = [self _ensureSetup];
   if (errorOut) {
     callback(@[@[errorOut]]);
     return;
   }
-  NSMutableArray *errors;
+  NSMutableArray<NSDictionary *> *errors;
   for (NSString *key in keys) {
-    id keyError = RCTErrorForKey(key);
+    NSDictionary *keyError = RCTErrorForKey(key);
     if (!keyError) {
       NSString *filePath = [self _filePathForKey:key];
       [[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
@@ -370,23 +372,19 @@ RCT_EXPORT_METHOD(multiRemove:(NSArray *)keys
     RCTAppendError(keyError, &errors);
   }
   [self _writeManifest:&errors];
-  if (callback) {
+  callback(@[RCTNullIfNil(errors)]);
-    callback(@[RCTNullIfNil(errors)]);
-  }
 }
 
 RCT_EXPORT_METHOD(clear:(RCTResponseSenderBlock)callback)
 {
   _manifest = [NSMutableDictionary new];
   NSError *error = RCTDeleteStorageDirectory();
-  if (callback) {
+  callback(@[RCTNullIfNil(error)]);
-    callback(@[RCTNullIfNil(error)]);
-  }
 }
 
 RCT_EXPORT_METHOD(getAllKeys:(RCTResponseSenderBlock)callback)
 {
-  id errorOut = [self _ensureSetup];
+  NSDictionary *errorOut = [self _ensureSetup];
   if (errorOut) {
     callback(@[errorOut, (id)kCFNull]);
   } else {

React/Modules/RCTDevMenu.m

@@ -138,8 +138,8 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   NSURLSessionDataTask *_updateTask;
   NSURL *_liveReloadURL;
   BOOL _jsLoaded;
-  NSArray *_presentedItems;
+  NSArray<RCTDevMenuItem *> *_presentedItems;
-  NSMutableArray *_extraMenuItems;
+  NSMutableArray<RCTDevMenuItem *> *_extraMenuItems;
 }
 
 @synthesize bridge = _bridge;
@@ -375,9 +375,9 @@ RCT_EXPORT_MODULE()
   [self settingsDidChange];
 }
 
-- (NSArray *)menuItems
+- (NSArray<RCTDevMenuItem *> *)menuItems
 {
-  NSMutableArray *items = [NSMutableArray new];
+  NSMutableArray<RCTDevMenuItem *> *items = [NSMutableArray new];
 
   // Add built-in items
 
@@ -435,7 +435,7 @@ RCT_EXPORT_METHOD(show)
   actionSheet.title = @"React Native: Development";
   actionSheet.delegate = self;
 
-  NSArray *items = [self menuItems];
+  NSArray<RCTDevMenuItem *> *items = [self menuItems];
   for (RCTDevMenuItem *item in items) {
     switch (item.type) {
       case RCTDevMenuTypeButton: {

React/Modules/RCTExceptionsManager.h

@@ -15,13 +15,14 @@
 
 // NOTE: Remove these three methods and the @optional directive after updating the codebase to use only the three below
 @optional
-- (void)handleSoftJSExceptionWithMessage:(NSString *)message stack:(NSArray *)stack;
-- (void)handleFatalJSExceptionWithMessage:(NSString *)message stack:(NSArray *)stack;
-- (void)updateJSExceptionWithMessage:(NSString *)message stack:(NSArray *)stack;
 
-- (void)handleSoftJSExceptionWithMessage:(NSString *)message stack:(NSArray *)stack exceptionId:(NSNumber *)exceptionId;
+- (void)handleSoftJSExceptionWithMessage:(NSString *)message stack:(NSArray<NSDictionary *> *)stack;
-- (void)handleFatalJSExceptionWithMessage:(NSString *)message stack:(NSArray *)stack exceptionId:(NSNumber *)exceptionId;
+- (void)handleFatalJSExceptionWithMessage:(NSString *)message stack:(NSArray<NSDictionary *> *)stack;
-- (void)updateJSExceptionWithMessage:(NSString *)message stack:(NSArray *)stack exceptionId:(NSNumber *)exceptionId;
+- (void)updateJSExceptionWithMessage:(NSString *)message stack:(NSArray<NSDictionary *> *)stack;
+
+- (void)handleSoftJSExceptionWithMessage:(NSString *)message stack:(NSArray<NSDictionary *> *)stack exceptionId:(NSNumber *)exceptionId;
+- (void)handleFatalJSExceptionWithMessage:(NSString *)message stack:(NSArray<NSDictionary *> *)stack exceptionId:(NSNumber *)exceptionId;
+- (void)updateJSExceptionWithMessage:(NSString *)message stack:(NSArray<NSDictionary *> *)stack exceptionId:(NSNumber *)exceptionId;
 
 @end
 

React/Modules/RCTExceptionsManager.m

@@ -9,6 +9,7 @@
 
 #import "RCTExceptionsManager.h"
 
+#import "RCTConvert.h"
 #import "RCTDefines.h"
 #import "RCTLog.h"
 #import "RCTRedBox.h"
@@ -39,7 +40,7 @@ RCT_EXPORT_MODULE()
 }
 
 RCT_EXPORT_METHOD(reportSoftException:(NSString *)message
-                  stack:(NSArray *)stack
+                  stack:(NSDictionaryArray *)stack
                   exceptionId:(nonnull NSNumber *)exceptionId)
 {
   // TODO(#7070533): report a soft error to the server
@@ -55,7 +56,7 @@ RCT_EXPORT_METHOD(reportSoftException:(NSString *)message
 }
 
 RCT_EXPORT_METHOD(reportFatalException:(NSString *)message
-                  stack:(NSArray *)stack
+                  stack:(NSDictionaryArray *)stack
                   exceptionId:(nonnull NSNumber *)exceptionId)
 {
   if (_delegate) {
@@ -98,7 +99,7 @@ RCT_EXPORT_METHOD(reportFatalException:(NSString *)message
 }
 
 RCT_EXPORT_METHOD(updateExceptionMessage:(NSString *)message
-                  stack:(NSArray *)stack
+                  stack:(NSDictionaryArray *)stack
                   exceptionId:(nonnull NSNumber *)exceptionId)
 {
   if (_delegate) {
@@ -115,7 +116,7 @@ RCT_EXPORT_METHOD(updateExceptionMessage:(NSString *)message
 
 // Deprecated.  Use reportFatalException directly instead.
 RCT_EXPORT_METHOD(reportUnhandledException:(NSString *)message
-                  stack:(NSArray *)stack)
+                  stack:(NSDictionaryArray *)stack)
 {
   [self reportFatalException:message stack:stack exceptionId:@-1];
 }

React/Modules/RCTRedBox.h

@@ -17,8 +17,8 @@
 - (void)showError:(NSError *)error;
 - (void)showErrorMessage:(NSString *)message;
 - (void)showErrorMessage:(NSString *)message withDetails:(NSString *)details;
-- (void)showErrorMessage:(NSString *)message withStack:(NSArray *)stack;
+- (void)showErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack;
-- (void)updateErrorMessage:(NSString *)message withStack:(NSArray *)stack;
+- (void)updateErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack;
 
 - (void)dismiss;
 

React/Modules/RCTRedBox.m

@@ -23,7 +23,7 @@
 {
   UITableView *_stackTraceTableView;
   NSString *_lastErrorMessage;
-  NSArray *_lastStackTrace;
+  NSArray<NSDictionary *> *_lastStackTrace;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame
@@ -103,7 +103,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   [[[NSURLSession sharedSession] dataTaskWithRequest:request] resume];
 }
 
-- (void)showErrorMessage:(NSString *)message withStack:(NSArray *)stack showIfHidden:(BOOL)shouldShow
+- (void)showErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack showIfHidden:(BOOL)shouldShow
 {
   if ((self.hidden && shouldShow) || (!self.hidden && [_lastErrorMessage isEqualToString:message])) {
     _lastStackTrace = stack;
@@ -225,7 +225,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
 #pragma mark - Key commands
 
-- (NSArray *)keyCommands
+- (NSArray<UIKeyCommand *> *)keyCommands
 {
   // NOTE: We could use RCTKeyCommands for this, but since
   // we control this window, we can use the standard, non-hacky
@@ -281,17 +281,17 @@ RCT_EXPORT_MODULE()
   [self showErrorMessage:combinedMessage];
 }
 
-- (void)showErrorMessage:(NSString *)message withStack:(NSArray *)stack
+- (void)showErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack
 {
   [self showErrorMessage:message withStack:stack showIfHidden:YES];
 }
 
-- (void)updateErrorMessage:(NSString *)message withStack:(NSArray *)stack
+- (void)updateErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack
 {
   [self showErrorMessage:message withStack:stack showIfHidden:NO];
 }
 
-- (void)showErrorMessage:(NSString *)message withStack:(NSArray *)stack showIfHidden:(BOOL)shouldShow
+- (void)showErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack showIfHidden:(BOOL)shouldShow
 {
   dispatch_async(dispatch_get_main_queue(), ^{
     if (!_window) {
@@ -332,9 +332,9 @@ RCT_EXPORT_MODULE()
 - (void)showError:(NSError *)message {}
 - (void)showErrorMessage:(NSString *)message {}
 - (void)showErrorMessage:(NSString *)message withDetails:(NSString *)details {}
-- (void)showErrorMessage:(NSString *)message withStack:(NSArray *)stack {}
+- (void)showErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack {}
-- (void)updateErrorMessage:(NSString *)message withStack:(NSArray *)stack {}
+- (void)updateErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack {}
-- (void)showErrorMessage:(NSString *)message withStack:(NSArray *)stack showIfHidden:(BOOL)shouldShow {}
+- (void)showErrorMessage:(NSString *)message withStack:(NSArray<NSDictionary *> *)stack showIfHidden:(BOOL)shouldShow {}
 - (void)dismiss {}
 
 @end

React/Modules/RCTTiming.m

@@ -145,7 +145,7 @@ RCT_EXPORT_MODULE()
 
 - (void)didUpdateFrame:(__unused RCTFrameUpdate *)update
 {
-  NSMutableArray *timersToCall = [NSMutableArray new];
+  NSMutableArray<NSNumber *> *timersToCall = [NSMutableArray new];
   for (RCTTimer *timer in _timers.allObjects) {
     if ([timer updateFoundNeedsJSUpdate]) {
       [timersToCall addObject:timer.callbackID];

React/Modules/RCTUIManager.m

@@ -191,8 +191,8 @@ static UIViewAnimationOptions UIViewAnimationOptionsFromRCTAnimationType(RCTAnim
   dispatch_queue_t _shadowQueue;
 
   // Root views are only mutated on the shadow queue
-  NSMutableSet *_rootViewTags;
+  NSMutableSet<NSNumber *> *_rootViewTags;
-  NSMutableArray *_pendingUIBlocks;
+  NSMutableArray<dispatch_block_t> *_pendingUIBlocks;
 
   // Animation
   RCTLayoutAnimation *_nextLayoutAnimation; // RCT thread only
@@ -201,7 +201,7 @@ static UIViewAnimationOptions UIViewAnimationOptionsFromRCTAnimationType(RCTAnim
   // Keyed by viewName
   NSDictionary *_componentDataByName;
 
-  NSMutableSet *_bridgeTransactionListeners;
+  NSMutableSet<id<RCTComponent>> *_bridgeTransactionListeners;
 }
 
 @synthesize bridge = _bridge;
@@ -396,7 +396,8 @@ extern NSString *RCTBridgeModuleNameForClass(Class cls);
 /**
  * Unregisters views from registries
  */
-- (void)_purgeChildren:(NSArray *)children fromRegistry:(RCTSparseArray *)registry
+- (void)_purgeChildren:(NSArray<id<RCTComponent>> *)children
+          fromRegistry:(RCTSparseArray *)registry
 {
   for (id<RCTComponent> child in children) {
     RCTTraverseViewNodes(registry[child.reactTag], ^(id<RCTComponent> subview) {
@@ -442,7 +443,7 @@ extern NSString *RCTBridgeModuleNameForClass(Class cls);
 {
   RCTAssert(![NSThread isMainThread], @"Should be called on shadow thread");
 
-  NSMutableSet *viewsWithNewFrames = [NSMutableSet setWithCapacity:1];
+  NSMutableSet<RCTShadowView *> *viewsWithNewFrames = [NSMutableSet setWithCapacity:1];
 
   // This is nuanced. In the JS thread, we create a new update buffer
   // `frameTags`/`frames` that is created/mutated in the JS thread. We access
@@ -452,10 +453,14 @@ extern NSString *RCTBridgeModuleNameForClass(Class cls);
   [rootShadowView collectRootUpdatedFrames:viewsWithNewFrames];
 
   // Parallel arrays are built and then handed off to main thread
-  NSMutableArray *frameReactTags = [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
+  NSMutableArray<NSNumber *> *frameReactTags =
-  NSMutableArray *frames = [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
+    [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
-  NSMutableArray *areNew = [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
+  NSMutableArray<NSValue *> *frames =
-  NSMutableArray *parentsAreNew = [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
+    [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
+  NSMutableArray<NSNumber *> *areNew =
+    [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
+  NSMutableArray<NSNumber *> *parentsAreNew =
+    [NSMutableArray arrayWithCapacity:viewsWithNewFrames.count];
 
   for (RCTShadowView *shadowView in viewsWithNewFrames) {
     [frameReactTags addObject:shadowView.reactTag];
@@ -473,7 +478,7 @@ extern NSString *RCTBridgeModuleNameForClass(Class cls);
   // reactSetFrame: has been called. Note that if reactSetFrame: is not called,
   // these won't be called either, so this is not a suitable place to update
   // properties that aren't related to layout.
-  NSMutableArray *updateBlocks = [NSMutableArray new];
+  NSMutableArray<RCTViewManagerUIBlock> *updateBlocks = [NSMutableArray new];
   for (RCTShadowView *shadowView in viewsWithNewFrames) {
     RCTViewManager *manager = [_componentDataByName[shadowView.viewName] manager];
     RCTViewManagerUIBlock block = [manager uiBlockToAmendWithShadowView:shadowView];
@@ -583,7 +588,7 @@ extern NSString *RCTBridgeModuleNameForClass(Class cls);
 
 - (void)_amendPendingUIBlocksWithStylePropagationUpdateForRootView:(RCTShadowView *)topView
 {
-  NSMutableSet *applierBlocks = [NSMutableSet setWithCapacity:1];
+  NSMutableSet<RCTApplierBlock> *applierBlocks = [NSMutableSet setWithCapacity:1];
   [topView collectUpdatedProperties:applierBlocks parentProperties:@{}];
 
   if (applierBlocks.count) {
@@ -605,7 +610,7 @@ RCT_EXPORT_METHOD(removeSubviewsFromContainerWithID:(nonnull NSNumber *)containe
   RCTAssert(container != nil, @"container view (for ID %@) not found", containerID);
 
   NSUInteger subviewsCount = [container reactSubviews].count;
-  NSMutableArray *indices = [[NSMutableArray alloc] initWithCapacity:subviewsCount];
+  NSMutableArray<NSNumber *> *indices = [[NSMutableArray alloc] initWithCapacity:subviewsCount];
   for (NSUInteger childIndex = 0; childIndex < subviewsCount; childIndex++) {
     [indices addObject:@(childIndex)];
   }
@@ -624,8 +629,8 @@ RCT_EXPORT_METHOD(removeSubviewsFromContainerWithID:(nonnull NSNumber *)containe
  *
  * @returns Array of removed items.
  */
-- (NSArray *)_childrenToRemoveFromContainer:(id<RCTComponent>)container
+- (NSArray<id<RCTComponent>> *)_childrenToRemoveFromContainer:(id<RCTComponent>)container
-                                  atIndices:(NSArray *)atIndices
+                                                    atIndices:(NSArray<NSNumber *> *)atIndices
 {
   // If there are no indices to move or the container has no subviews don't bother
   // We support parents with nil subviews so long as they're all nil so this allows for this behavior
@@ -633,7 +638,7 @@ RCT_EXPORT_METHOD(removeSubviewsFromContainerWithID:(nonnull NSNumber *)containe
     return nil;
   }
   // Construction of removed children must be done "up front", before indices are disturbed by removals.
-  NSMutableArray *removedChildren = [NSMutableArray arrayWithCapacity:atIndices.count];
+  NSMutableArray<id<RCTComponent>> *removedChildren = [NSMutableArray arrayWithCapacity:atIndices.count];
   RCTAssert(container != nil, @"container view (for ID %@) not found", container);
   for (NSNumber *indexNumber in atIndices) {
     NSUInteger index = indexNumber.unsignedIntegerValue;
@@ -648,9 +653,10 @@ RCT_EXPORT_METHOD(removeSubviewsFromContainerWithID:(nonnull NSNumber *)containe
   return removedChildren;
 }
 
-- (void)_removeChildren:(NSArray *)children fromContainer:(id<RCTComponent>)container
+- (void)_removeChildren:(NSArray<id<RCTComponent>> *)children
+          fromContainer:(id<RCTComponent>)container
 {
-  for (id removedChild in children) {
+  for (id<RCTComponent> removedChild in children) {
     [container removeReactSubview:removedChild];
   }
 }
@@ -659,14 +665,14 @@ RCT_EXPORT_METHOD(removeRootView:(nonnull NSNumber *)rootReactTag)
 {
   RCTShadowView *rootShadowView = _shadowViewRegistry[rootReactTag];
   RCTAssert(rootShadowView.superview == nil, @"root view cannot have superview (ID %@)", rootReactTag);
-  [self _purgeChildren:rootShadowView.reactSubviews fromRegistry:_shadowViewRegistry];
+  [self _purgeChildren:(NSArray<id<RCTComponent>> *)rootShadowView.reactSubviews fromRegistry:_shadowViewRegistry];
    _shadowViewRegistry[rootReactTag] = nil;
   [_rootViewTags removeObject:rootReactTag];
 
   [self addUIBlock:^(RCTUIManager *uiManager, RCTSparseArray *viewRegistry){
     RCTAssertMainThread();
     UIView *rootView = viewRegistry[rootReactTag];
-    [uiManager _purgeChildren:rootView.reactSubviews fromRegistry:viewRegistry];
+    [uiManager _purgeChildren:(NSArray<id<RCTComponent>> *)rootView.reactSubviews fromRegistry:viewRegistry];
     viewRegistry[rootReactTag] = nil;
 
     [[NSNotificationCenter defaultCenter] postNotificationName:RCTUIManagerDidRemoveRootViewNotification
@@ -675,7 +681,8 @@ RCT_EXPORT_METHOD(removeRootView:(nonnull NSNumber *)rootReactTag)
   }];
 }
 
-RCT_EXPORT_METHOD(replaceExistingNonRootView:(nonnull NSNumber *)reactTag withView:(nonnull NSNumber *)newReactTag)
+RCT_EXPORT_METHOD(replaceExistingNonRootView:(nonnull NSNumber *)reactTag
+                  withView:(nonnull NSNumber *)newReactTag)
 {
   RCTShadowView *shadowView = _shadowViewRegistry[reactTag];
   RCTAssert(shadowView != nil, @"shadowView (for ID %@) not found", reactTag);
@@ -685,8 +692,8 @@ RCT_EXPORT_METHOD(replaceExistingNonRootView:(nonnull NSNumber *)reactTag withVi
 
   NSUInteger indexOfView = [superShadowView.reactSubviews indexOfObject:shadowView];
   RCTAssert(indexOfView != NSNotFound, @"View's superview doesn't claim it as subview (id %@)", reactTag);
-  NSArray *removeAtIndices = @[@(indexOfView)];
+  NSArray<NSNumber *> *removeAtIndices = @[@(indexOfView)];
-  NSArray *addTags = @[newReactTag];
+  NSArray<NSNumber *> *addTags = @[newReactTag];
   [self manageChildren:superShadowView.reactTag
         moveFromIndices:nil
           moveToIndices:nil
@@ -696,11 +703,11 @@ RCT_EXPORT_METHOD(replaceExistingNonRootView:(nonnull NSNumber *)reactTag withVi
 }
 
 RCT_EXPORT_METHOD(manageChildren:(nonnull NSNumber *)containerReactTag
-                  moveFromIndices:(NSArray *)moveFromIndices
+                  moveFromIndices:(NSNumberArray *)moveFromIndices
-                  moveToIndices:(NSArray *)moveToIndices
+                  moveToIndices:(NSNumberArray *)moveToIndices
-                  addChildReactTags:(NSArray *)addChildReactTags
+                  addChildReactTags:(NSNumberArray *)addChildReactTags
-                  addAtIndices:(NSArray *)addAtIndices
+                  addAtIndices:(NSNumberArray *)addAtIndices
-                  removeAtIndices:(NSArray *)removeAtIndices)
+                  removeAtIndices:(NSNumberArray *)removeAtIndices)
 {
   [self _manageChildren:containerReactTag
         moveFromIndices:moveFromIndices
@@ -722,11 +729,11 @@ RCT_EXPORT_METHOD(manageChildren:(nonnull NSNumber *)containerReactTag
 }
 
 - (void)_manageChildren:(NSNumber *)containerReactTag
-        moveFromIndices:(NSArray *)moveFromIndices
+        moveFromIndices:(NSArray<NSNumber *> *)moveFromIndices
-          moveToIndices:(NSArray *)moveToIndices
+          moveToIndices:(NSArray<NSNumber *> *)moveToIndices
-      addChildReactTags:(NSArray *)addChildReactTags
+      addChildReactTags:(NSArray<NSNumber *> *)addChildReactTags
-           addAtIndices:(NSArray *)addAtIndices
+           addAtIndices:(NSArray<NSNumber *> *)addAtIndices
-        removeAtIndices:(NSArray *)removeAtIndices
+        removeAtIndices:(NSArray<NSNumber *> *)removeAtIndices
                registry:(RCTSparseArray *)registry
 {
   id<RCTComponent> container = registry[containerReactTag];
@@ -734,8 +741,10 @@ RCT_EXPORT_METHOD(manageChildren:(nonnull NSNumber *)containerReactTag
   RCTAssert(addChildReactTags.count == addAtIndices.count, @"there should be at least one React child to add");
 
   // Removes (both permanent and temporary moves) are using "before" indices
-  NSArray *permanentlyRemovedChildren = [self _childrenToRemoveFromContainer:container atIndices:removeAtIndices];
+  NSArray<id<RCTComponent>> *permanentlyRemovedChildren =
-  NSArray *temporarilyRemovedChildren = [self _childrenToRemoveFromContainer:container atIndices:moveFromIndices];
+    [self _childrenToRemoveFromContainer:container atIndices:removeAtIndices];
+  NSArray<id<RCTComponent>> *temporarilyRemovedChildren =
+    [self _childrenToRemoveFromContainer:container atIndices:moveFromIndices];
   [self _removeChildren:permanentlyRemovedChildren fromContainer:container];
   [self _removeChildren:temporarilyRemovedChildren fromContainer:container];
 
@@ -749,15 +758,17 @@ RCT_EXPORT_METHOD(manageChildren:(nonnull NSNumber *)containerReactTag
     destinationsToChildrenToAdd[moveToIndices[index]] = temporarilyRemovedChildren[index];
   }
   for (NSInteger index = 0, length = addAtIndices.count; index < length; index++) {
-    id view = registry[addChildReactTags[index]];
+    id<RCTComponent> view = registry[addChildReactTags[index]];
     if (view) {
       destinationsToChildrenToAdd[addAtIndices[index]] = view;
     }
   }
 
-  NSArray *sortedIndices = [destinationsToChildrenToAdd.allKeys sortedArrayUsingSelector:@selector(compare:)];
+  NSArray<NSNumber *> *sortedIndices =
+    [destinationsToChildrenToAdd.allKeys sortedArrayUsingSelector:@selector(compare:)];
   for (NSNumber *reactIndex in sortedIndices) {
-    [container insertReactSubview:destinationsToChildrenToAdd[reactIndex] atIndex:reactIndex.integerValue];
+    [container insertReactSubview:destinationsToChildrenToAdd[reactIndex]
+                          atIndex:reactIndex.integerValue];
   }
 }
 
@@ -894,7 +905,7 @@ RCT_EXPORT_METHOD(findSubviewIn:(nonnull NSNumber *)reactTag atPoint:(CGPoint)po
   // First copy the previous blocks into a temporary variable, then reset the
   // pending blocks to a new array. This guards against mutation while
   // processing the pending blocks in another thread.
-  NSArray *previousPendingUIBlocks = _pendingUIBlocks;
+  NSArray<dispatch_block_t> *previousPendingUIBlocks = _pendingUIBlocks;
   _pendingUIBlocks = [NSMutableArray new];
 
   if (previousPendingUIBlocks.count) {
@@ -1036,8 +1047,9 @@ RCT_EXPORT_METHOD(measureViewsInRect:(CGRect)rect
     RCTLogError(@"Attempting to measure view that does not exist (tag #%@)", reactTag);
     return;
   }
-  NSArray *childShadowViews = [shadowView reactSubviews];
+  NSArray<RCTShadowView *> *childShadowViews = [shadowView reactSubviews];
-  NSMutableArray *results = [[NSMutableArray alloc] initWithCapacity:childShadowViews.count];
+  NSMutableArray<NSDictionary *> *results =
+    [[NSMutableArray alloc] initWithCapacity:childShadowViews.count];
 
   [childShadowViews enumerateObjectsUsingBlock:
    ^(RCTShadowView *childShadowView, NSUInteger idx, __unused BOOL *stop) {

React/Profiler/RCTPerfMonitor.m

@@ -424,7 +424,7 @@ RCT_EXPORT_MODULE()
     _remaining = nil;
   }
 
-  NSArray *lines = [log componentsSeparatedByString:@"\n"];
+  NSArray<NSString *> *lines = [log componentsSeparatedByString:@"\n"];
   if (lines.count == 1) { // no newlines
     _remaining = log;
     return;

React/Profiler/RCTProfile.m

@@ -336,10 +336,11 @@ NSString *RCTProfileEnd(RCTBridge *bridge)
   }
 }
 
-static NSMutableArray *RCTProfileGetThreadEvents(void)
+static NSMutableArray<NSArray *> *RCTProfileGetThreadEvents(void)
 {
   static NSString *const RCTProfileThreadEventsKey = @"RCTProfileThreadEventsKey";
-  NSMutableArray *threadEvents = [NSThread currentThread].threadDictionary[RCTProfileThreadEventsKey];
+  NSMutableArray<NSArray *> *threadEvents =
+    [NSThread currentThread].threadDictionary[RCTProfileThreadEventsKey];
   if (!threadEvents) {
     threadEvents = [NSMutableArray new];
     [NSThread currentThread].threadDictionary[RCTProfileThreadEventsKey] = threadEvents;
@@ -377,7 +378,7 @@ void RCTProfileEndEvent(
     return;
   }
 
-  NSMutableArray *events = RCTProfileGetThreadEvents();
+  NSMutableArray<NSArray *> *events = RCTProfileGetThreadEvents();
   NSArray *event = events.lastObject;
   [events removeLastObject];
 

React/Views/RCTComponent.h

@@ -27,7 +27,7 @@ typedef void (^RCTBubblingEventBlock)(NSDictionary *body);
 
 - (void)insertReactSubview:(id<RCTComponent>)subview atIndex:(NSInteger)atIndex;
 - (void)removeReactSubview:(id<RCTComponent>)subview;
-- (NSArray *)reactSubviews;
+- (NSArray<id<RCTComponent>> *)reactSubviews;
 - (id<RCTComponent>)reactSuperview;
 - (NSNumber *)reactTagAtPoint:(CGPoint)point;
 

React/Views/RCTComponentData.m

@@ -100,7 +100,8 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
     SEL selector = NSSelectorFromString([NSString stringWithFormat:@"propConfig%@_%@", shadowView ? @"Shadow" : @"", name]);
     Class managerClass = [_manager class];
     if ([managerClass respondsToSelector:selector]) {
-      NSArray *typeAndKeyPath = ((NSArray *(*)(id, SEL))objc_msgSend)(managerClass, selector);
+      NSArray<NSString *> *typeAndKeyPath =
+        ((NSArray<NSString *> *(*)(id, SEL))objc_msgSend)(managerClass, selector);
       type = NSSelectorFromString([typeAndKeyPath[0] stringByAppendingString:@":"]);
       keyPath = typeAndKeyPath.count > 1 ? typeAndKeyPath[1] : nil;
     } else {
@@ -125,7 +126,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
       // Disect keypath
       NSString *key = name;
-      NSArray *parts = [keyPath componentsSeparatedByString:@"."];
+      NSArray<NSString *> *parts = [keyPath componentsSeparatedByString:@"."];
       if (parts) {
         key = parts.lastObject;
         parts = [parts subarrayWithRange:(NSRange){0, parts.count - 1}];
@@ -312,9 +313,9 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 {
   Class managerClass = [_manager class];
 
-  NSMutableArray *directEvents = [NSMutableArray new];
+  NSMutableArray<NSString *> *directEvents = [NSMutableArray new];
   if (RCTClassOverridesInstanceMethod(managerClass, @selector(customDirectEventTypes))) {
-    NSArray *events = [_manager customDirectEventTypes];
+    NSArray<NSString *> *events = [_manager customDirectEventTypes];
     if (RCT_DEBUG) {
       RCTAssert(!events || [events isKindOfClass:[NSArray class]],
         @"customDirectEventTypes must return an array, but %@ returned %@",
@@ -325,9 +326,9 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
     }
   }
 
-  NSMutableArray *bubblingEvents = [NSMutableArray new];
+  NSMutableArray<NSString *> *bubblingEvents = [NSMutableArray new];
   if (RCTClassOverridesInstanceMethod(managerClass, @selector(customBubblingEventTypes))) {
-        NSArray *events = [_manager customBubblingEventTypes];
+    NSArray<NSString *> *events = [_manager customBubblingEventTypes];
     if (RCT_DEBUG) {
       RCTAssert(!events || [events isKindOfClass:[NSArray class]],
         @"customBubblingEventTypes must return an array, but %@ returned %@",
@@ -349,7 +350,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
       NSRange nameRange = [methodName rangeOfString:@"_"];
       if (nameRange.length) {
         NSString *name = [methodName substringFromIndex:nameRange.location + 1];
-        NSString *type = ((NSArray *(*)(id, SEL))objc_msgSend)(managerClass, selector)[0];
+        NSString *type = ((NSArray<NSString *> *(*)(id, SEL))objc_msgSend)(managerClass, selector)[0];
         if (RCT_DEBUG && propTypes[name] && ![propTypes[name] isEqualToString:type]) {
           RCTLogError(@"Property '%@' of component '%@' redefined from '%@' "
                       "to '%@'", name, _name, propTypes[name], type);

React/Views/RCTMap.h

@@ -25,7 +25,7 @@ extern const CGFloat RCTMapZoomBoundBuffer;
 @property (nonatomic, assign) CGFloat maxDelta;
 @property (nonatomic, assign) UIEdgeInsets legalLabelInsets;
 @property (nonatomic, strong) NSTimer *regionChangeObserveTimer;
-@property (nonatomic, strong) NSMutableArray *annotationIds;
+@property (nonatomic, copy) NSArray<NSString *> *annotationIds;
 
 @property (nonatomic, copy) RCTBubblingEventBlock onChange;
 @property (nonatomic, copy) RCTBubblingEventBlock onPress;

React/Views/RCTMap.m

@@ -109,9 +109,9 @@ const CGFloat RCTMapZoomBoundBuffer = 0.01;
 
 - (void)setAnnotations:(RCTPointAnnotationArray *)annotations
 {
-  NSMutableArray *newAnnotationIds = [NSMutableArray new];
+  NSMutableArray<NSString *> *newAnnotationIds = [NSMutableArray new];
-  NSMutableArray *annotationsToDelete = [NSMutableArray new];
+  NSMutableArray<RCTPointAnnotation *> *annotationsToDelete = [NSMutableArray new];
-  NSMutableArray *annotationsToAdd = [NSMutableArray new];
+  NSMutableArray<RCTPointAnnotation *> *annotationsToAdd = [NSMutableArray new];
 
   for (RCTPointAnnotation *annotation in annotations) {
     if (![annotation isKindOfClass:[RCTPointAnnotation class]]) {
@@ -138,19 +138,19 @@ const CGFloat RCTMapZoomBoundBuffer = 0.01;
   }
 
   if (annotationsToDelete.count) {
-    [self removeAnnotations:annotationsToDelete];
+    [self removeAnnotations:(NSArray<id<MKAnnotation>> *)annotationsToDelete];
   }
 
   if (annotationsToAdd.count) {
-    [self addAnnotations:annotationsToAdd];
+    [self addAnnotations:(NSArray<id<MKAnnotation>> *)annotationsToAdd];
   }
 
-  NSMutableArray *newIds = [NSMutableArray new];
+  NSMutableArray<NSString *> *newIds = [NSMutableArray new];
-  for (RCTPointAnnotation *anno in self.annotations) {
+  for (RCTPointAnnotation *annotation in self.annotations) {
-    if ([anno isKindOfClass:[MKUserLocation class]]) {
+    if ([annotation isKindOfClass:[MKUserLocation class]]) {
       continue;
     }
-    [newIds addObject:anno.identifier];
+    [newIds addObject:annotation.identifier];
   }
   self.annotationIds = newIds;
 }

React/Views/RCTModalHostView.m

@@ -51,18 +51,18 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:coder)
   }
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<UIView<RCTComponent> *> *)reactSubviews
 {
-  return [NSArray arrayWithObjects:_modalViewController.view, nil];
+  return _modalViewController.view ? @[_modalViewController.view] : @[];
 }
 
-- (void)insertReactSubview:(UIView *)subview atIndex:(__unused NSInteger)atIndex
+- (void)insertReactSubview:(UIView<RCTComponent> *)subview atIndex:(__unused NSInteger)atIndex
 {
   [subview addGestureRecognizer:_touchHandler];
   _modalViewController.view = subview;
 }
 
-- (void)removeReactSubview:(UIView *)subview
+- (void)removeReactSubview:(UIView<RCTComponent> *)subview
 {
   RCTAssert(subview == _modalViewController.view, @"Cannot remove view other than modal view");
   _modalViewController.view = nil;

React/Views/RCTNavigator.m

@@ -200,8 +200,8 @@ NSInteger kNeverProgressed = -10000;
 
 // Previous views are only mainted in order to detect incorrect
 // addition/removal of views below the `requestedTopOfStack`
-@property (nonatomic, copy, readwrite) NSArray *previousViews;
+@property (nonatomic, copy, readwrite) NSArray<RCTNavItem *> *previousViews;
-@property (nonatomic, readwrite, strong) NSMutableArray *currentViews;
+@property (nonatomic, readwrite, strong) NSMutableArray<RCTNavItem *> *currentViews;
 @property (nonatomic, readwrite, strong) RCTNavigationController *navigationController;
 /**
  * Display link is used to get high frequency sample rate during
@@ -400,7 +400,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
  * `requestedTopOfStack` changes, there had better be enough subviews present
  * to satisfy the push/pop.
  */
-- (void)insertReactSubview:(UIView *)view atIndex:(NSInteger)atIndex
+- (void)insertReactSubview:(RCTNavItem *)view atIndex:(NSInteger)atIndex
 {
   RCTAssert([view isKindOfClass:[RCTNavItem class]], @"RCTNavigator only accepts RCTNavItem subviews");
   RCTAssert(
@@ -410,7 +410,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   [_currentViews insertObject:view atIndex:atIndex];
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<RCTNavItem *> *)reactSubviews
 {
   return _currentViews;
 }
@@ -422,7 +422,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   _navigationController.view.frame = self.bounds;
 }
 
-- (void)removeReactSubview:(UIView *)subview
+- (void)removeReactSubview:(RCTNavItem *)subview
 {
   if (_currentViews.count <= 0 || subview == _currentViews[0]) {
     RCTLogError(@"Attempting to remove invalid RCT subview of RCTNavigator");

React/Views/RCTPicker.h

@@ -9,6 +9,12 @@
 
 #import <UIKit/UIKit.h>
 
+#import "UIView+React.h"
+
 @interface RCTPicker : UIPickerView
 
+@property (nonatomic, copy) NSArray<NSDictionary *> *items;
+@property (nonatomic, assign) NSInteger selectedIndex;
+@property (nonatomic, copy) RCTBubblingEventBlock onChange;
+
 @end

React/Views/RCTPicker.m

@@ -10,14 +10,8 @@
 #import "RCTPicker.h"
 
 #import "RCTUtils.h"
-#import "UIView+React.h"
 
 @interface RCTPicker() <UIPickerViewDataSource, UIPickerViewDelegate>
-
-@property (nonatomic, copy) NSArray *items;
-@property (nonatomic, assign) NSInteger selectedIndex;
-@property (nonatomic, copy) RCTBubblingEventBlock onChange;
-
 @end
 
 @implementation RCTPicker
@@ -33,7 +27,7 @@
 
 RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
-- (void)setItems:(NSArray *)items
+- (void)setItems:(NSArray<NSDictionary *> *)items
 {
   _items = [items copy];
   [self setNeedsLayout];

React/Views/RCTScrollView.m

@@ -117,7 +117,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
 - (RCTScrollEvent *)coalesceWithEvent:(RCTScrollEvent *)newEvent
 {
-  NSArray *updatedChildFrames = [_userData[@"updatedChildFrames"] arrayByAddingObjectsFromArray:newEvent->_userData[@"updatedChildFrames"]];
+  NSArray<NSDictionary *> *updatedChildFrames = [_userData[@"updatedChildFrames"] arrayByAddingObjectsFromArray:newEvent->_userData[@"updatedChildFrames"]];
 
   if (updatedChildFrames) {
     NSMutableDictionary *userData = [newEvent->_userData mutableCopy];
@@ -360,7 +360,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   RCTCustomScrollView *_scrollView;
   UIView *_contentView;
   NSTimeInterval _lastScrollDispatchTime;
-  NSMutableArray *_cachedChildFrames;
+  NSMutableArray<NSValue *> *_cachedChildFrames;
   BOOL _allowNextScrollNoMatterWhat;
   CGRect _lastClippedToRect;
 }
@@ -412,7 +412,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   [subview removeFromSuperview];
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<UIView<RCTComponent> *> *)reactSubviews
 {
   return _contentView ? @[_contentView] : @[];
 }
@@ -564,7 +564,7 @@ RCT_SCROLL_EVENT_HANDLER(scrollViewDidZoom, RCTScrollEventTypeMove)
       (_scrollEventThrottle > 0 && _scrollEventThrottle < (now - _lastScrollDispatchTime))) {
 
     // Calculate changed frames
-    NSArray *childFrames = [self calculateChildFramesData];
+    NSArray<NSDictionary *> *childFrames = [self calculateChildFramesData];
 
     // Dispatch event
     [_eventDispatcher sendScrollEventWithType:RCTScrollEventTypeMove
@@ -579,9 +579,9 @@ RCT_SCROLL_EVENT_HANDLER(scrollViewDidZoom, RCTScrollEventTypeMove)
   RCT_FORWARD_SCROLL_EVENT(scrollViewDidScroll:scrollView);
 }
 
-- (NSArray *)calculateChildFramesData
+- (NSArray<NSDictionary *> *)calculateChildFramesData
 {
-    NSMutableArray *updatedChildFrames = [NSMutableArray new];
+    NSMutableArray<NSDictionary *> *updatedChildFrames = [NSMutableArray new];
     [[_contentView reactSubviews] enumerateObjectsUsingBlock:
      ^(UIView *subview, NSUInteger idx, __unused BOOL *stop) {
 

React/Views/RCTScrollViewManager.m

@@ -16,7 +16,7 @@
 
 @interface RCTScrollView (Private)
 
-- (NSArray *)calculateChildFramesData;
+- (NSArray<NSDictionary *> *)calculateChildFramesData;
 
 @end
 
@@ -83,13 +83,13 @@ RCT_EXPORT_METHOD(getContentSize:(nonnull NSNumber *)reactTag
 {
   [self.bridge.uiManager addUIBlock:^(__unused RCTUIManager *uiManager, RCTSparseArray *viewRegistry) {
 
-    UIView *view = viewRegistry[reactTag];
+    RCTScrollView *view = viewRegistry[reactTag];
-    if (!view) {
+    if (!view || ![view isKindOfClass:[RCTScrollView class]]) {
-      RCTLogError(@"Cannot find view with tag #%@", reactTag);
+      RCTLogError(@"Cannot find RCTScrollView with tag #%@", reactTag);
       return;
     }
 
-    CGSize size = ((RCTScrollView *)view).scrollView.contentSize;
+    CGSize size = view.scrollView.contentSize;
     callback(@[@{
       @"width" : @(size.width),
       @"height" : @(size.height)
@@ -102,20 +102,20 @@ RCT_EXPORT_METHOD(calculateChildFrames:(nonnull NSNumber *)reactTag
 {
   [self.bridge.uiManager addUIBlock:^(__unused RCTUIManager *uiManager, RCTSparseArray *viewRegistry) {
 
-    UIView *view = viewRegistry[reactTag];
+    RCTScrollView *view = viewRegistry[reactTag];
-    if (!view) {
+    if (!view || ![view isKindOfClass:[RCTScrollView class]]) {
-      RCTLogError(@"Cannot find view with tag #%@", reactTag);
+      RCTLogError(@"Cannot find RCTScrollView with tag #%@", reactTag);
       return;
     }
 
-    NSArray *childFrames = [((RCTScrollView *)view) calculateChildFramesData];
+    NSArray<NSDictionary *> *childFrames = [view calculateChildFramesData];
     if (childFrames) {
       callback(@[childFrames]);
     }
   }];
 }
 
-- (NSArray *)customDirectEventTypes
+- (NSArray<NSString *> *)customDirectEventTypes
 {
   return @[
     @"scrollBeginDrag",

React/Views/RCTSegmentedControl.h

@@ -13,7 +13,7 @@
 
 @interface RCTSegmentedControl : UISegmentedControl
 
-@property (nonatomic, copy) NSArray *values;
+@property (nonatomic, copy) NSArray<NSString *> *values;
 @property (nonatomic, assign) NSInteger selectedIndex;
 @property (nonatomic, copy) RCTBubblingEventBlock onChange;
 

React/Views/RCTSegmentedControl.m

@@ -25,7 +25,7 @@
   return self;
 }
 
-- (void)setValues:(NSArray *)values
+- (void)setValues:(NSArray<NSString *> *)values
 {
   _values = [values copy];
   [self removeAllSegments];

React/Views/RCTShadowView.h

@@ -35,6 +35,9 @@ typedef void (^RCTApplierBlock)(RCTSparseArray *viewRegistry);
  */
 @interface RCTShadowView : NSObject <RCTComponent>
 
+- (NSArray<RCTShadowView *> *)reactSubviews;
+- (RCTShadowView *)reactSuperview;
+
 @property (nonatomic, weak, readonly) RCTShadowView *superview;
 @property (nonatomic, assign, readonly) css_node_t *cssNode;
 @property (nonatomic, copy) NSString *viewName;
@@ -120,27 +123,27 @@ typedef void (^RCTApplierBlock)(RCTSparseArray *viewRegistry);
  * The applierBlocks set contains RCTApplierBlock functions that must be applied
  * on the main thread in order to update the view.
  */
-- (void)collectUpdatedProperties:(NSMutableSet *)applierBlocks
+- (void)collectUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                 parentProperties:(NSDictionary *)parentProperties;
 
 /**
  * Process the updated properties and apply them to view. Shadow view classes
  * that add additional propagating properties should override this method.
  */
-- (NSDictionary *)processUpdatedProperties:(NSMutableSet *)applierBlocks
+- (NSDictionary *)processUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                           parentProperties:(NSDictionary *)parentProperties NS_REQUIRES_SUPER;
 
 /**
  * Calculate all views whose frame needs updating after layout has been calculated.
  * The viewsWithNewFrame set contains the reactTags of the views that need updating.
  */
-- (void)collectRootUpdatedFrames:(NSMutableSet *)viewsWithNewFrame;
+- (void)collectRootUpdatedFrames:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame;
 
 /**
  * Recursively apply layout to children.
  */
 - (void)applyLayoutNode:(css_node_t *)node
-      viewsWithNewFrame:(NSMutableSet *)viewsWithNewFrame
+      viewsWithNewFrame:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
        absolutePosition:(CGPoint)absolutePosition NS_REQUIRES_SUPER;
 
 /**

React/Views/RCTShadowView.m

@@ -36,7 +36,7 @@ typedef NS_ENUM(unsigned int, meta_prop_t) {
   RCTUpdateLifecycle _propagationLifecycle;
   RCTUpdateLifecycle _textLifecycle;
   NSDictionary *_lastParentProperties;
-  NSMutableArray *_reactSubviews;
+  NSMutableArray<RCTShadowView *> *_reactSubviews;
   BOOL _recomputePadding;
   BOOL _recomputeMargin;
   BOOL _recomputeBorder;
@@ -123,7 +123,7 @@ static void RCTProcessMetaProps(const float metaProps[META_PROP_COUNT], float st
 // You'll notice that this is the same width we calculated for the parent view because we've taken its position into account.
 
 - (void)applyLayoutNode:(css_node_t *)node
-      viewsWithNewFrame:(NSMutableSet *)viewsWithNewFrame
+      viewsWithNewFrame:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
        absolutePosition:(CGPoint)absolutePosition
 {
   if (!node->layout.should_update) {
@@ -171,7 +171,7 @@ static void RCTProcessMetaProps(const float metaProps[META_PROP_COUNT], float st
   }
 }
 
-- (NSDictionary *)processUpdatedProperties:(NSMutableSet *)applierBlocks
+- (NSDictionary *)processUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                           parentProperties:(NSDictionary *)parentProperties
 {
   // TODO: we always refresh all propagated properties when propagation is
@@ -201,7 +201,7 @@ static void RCTProcessMetaProps(const float metaProps[META_PROP_COUNT], float st
   return parentProperties;
 }
 
-- (void)collectUpdatedProperties:(NSMutableSet *)applierBlocks
+- (void)collectUpdatedProperties:(NSMutableSet<RCTApplierBlock> *)applierBlocks
                 parentProperties:(NSDictionary *)parentProperties
 {
   if (_propagationLifecycle == RCTUpdateLifecycleComputed && [parentProperties isEqualToDictionary:_lastParentProperties]) {
@@ -234,7 +234,7 @@ static void RCTProcessMetaProps(const float metaProps[META_PROP_COUNT], float st
   }
 }
 
-- (void)collectRootUpdatedFrames:(NSMutableSet *)viewsWithNewFrame
+- (void)collectRootUpdatedFrames:(NSMutableSet<RCTShadowView *> *)viewsWithNewFrame
 {
   RCTAssert(RCTIsReactRootView(self.reactTag),
             @"The method has been called on a view with react tag %@, which is not a root view", self.reactTag);
@@ -367,7 +367,7 @@ static void RCTProcessMetaProps(const float metaProps[META_PROP_COUNT], float st
   _cssNode->children_count = (int)_reactSubviews.count;
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<RCTShadowView *> *)reactSubviews
 {
   return _reactSubviews;
 }

React/Views/RCTTabBar.m

@@ -26,7 +26,7 @@
 {
   BOOL _tabsChanged;
   UITabBarController *_tabController;
-  NSMutableArray *_tabViews;
+  NSMutableArray<RCTTabBarItem *> *_tabViews;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame
@@ -52,12 +52,12 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   _tabController.delegate = nil;
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<RCTTabBarItem *> *)reactSubviews
 {
   return _tabViews;
 }
 
-- (void)insertReactSubview:(UIView *)view atIndex:(NSInteger)atIndex
+- (void)insertReactSubview:(RCTTabBarItem *)view atIndex:(NSInteger)atIndex
 {
   if (![view isKindOfClass:[RCTTabBarItem class]]) {
     RCTLogError(@"subview should be of type RCTTabBarItem");
@@ -67,7 +67,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
   _tabsChanged = YES;
 }
 
-- (void)removeReactSubview:(UIView *)subview
+- (void)removeReactSubview:(RCTTabBarItem *)subview
 {
   if (_tabViews.count == 0) {
     RCTLogError(@"should have at least one view to remove a subview");
@@ -92,7 +92,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 
   if (_tabsChanged) {
 
-    NSMutableArray *viewControllers = [NSMutableArray array];
+    NSMutableArray<UIViewController *> *viewControllers = [NSMutableArray array];
     for (RCTTabBarItem *tab in [self reactSubviews]) {
       UIViewController *controller = tab.reactViewController;
       if (!controller) {
@@ -105,7 +105,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
     _tabsChanged = NO;
   }
 
-  [[self reactSubviews] enumerateObjectsUsingBlock:
+  [_tabViews enumerateObjectsUsingBlock:
    ^(RCTTabBarItem *tab, NSUInteger index, __unused BOOL *stop) {
     UIViewController *controller = _tabController.viewControllers[index];
     controller.tabBarItem = tab.barItem;
@@ -148,7 +148,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
 - (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController
 {
   NSUInteger index = [tabBarController.viewControllers indexOfObject:viewController];
-  RCTTabBarItem *tab = [self reactSubviews][index];
+  RCTTabBarItem *tab = _tabViews[index];
   if (tab.onPress) tab.onPress(nil);
   return NO;
 }

React/Views/RCTView.m

@@ -92,7 +92,7 @@ static NSString *RCTRecursiveAccessibilityLabel(UIView *view)
 
 @implementation RCTView
 {
-  NSMutableArray *_reactSubviews;
+  NSMutableArray<UIView<RCTComponent> *> *_reactSubviews;
   UIColor *_backgroundColor;
 }
 
@@ -413,7 +413,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:unused)
   [subview removeFromSuperview];
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<UIView<RCTComponent> *> *)reactSubviews
 {
   // The _reactSubviews array is only used when we have hidden
   // offscreen views. If _reactSubviews is nil, we can assume

React/Views/RCTViewManager.h

@@ -70,7 +70,7 @@ typedef void (^RCTViewManagerUIBlock)(RCTUIManager *uiManager, RCTSparseArray *v
  * Note that this method is not inherited when you subclass a view module, and
  * you should not call [super customBubblingEventTypes] when overriding it.
  */
-- (NSArray *)customBubblingEventTypes;
+- (NSArray<NSString *> *)customBubblingEventTypes;
 
 /**
  * DEPRECATED: declare properties of type RCTDirectEventBlock instead
@@ -83,7 +83,7 @@ typedef void (^RCTViewManagerUIBlock)(RCTUIManager *uiManager, RCTSparseArray *v
  * Note that this method is not inherited when you subclass a view module, and
  * you should not call [super customDirectEventTypes] when overriding it.
  */
-- (NSArray *)customDirectEventTypes;
+- (NSArray<NSString *> *)customDirectEventTypes;
 
 /**
  * Called to notify manager that layout has finished, in case any calculated
@@ -103,13 +103,13 @@ typedef void (^RCTViewManagerUIBlock)(RCTUIManager *uiManager, RCTSparseArray *v
  * This handles the simple case, where JS and native property names match.
  */
 #define RCT_EXPORT_VIEW_PROPERTY(name, type) \
-+ (NSArray *)propConfig_##name { return @[@#type]; }
++ (NSArray<NSString *> *)propConfig_##name { return @[@#type]; }
 
 /**
  * This macro maps a named property to an arbitrary key path in the view.
  */
 #define RCT_REMAP_VIEW_PROPERTY(name, keyPath, type) \
-+ (NSArray *)propConfig_##name { return @[@#type, @#keyPath]; }
++ (NSArray<NSString *> *)propConfig_##name { return @[@#type, @#keyPath]; }
 
 /**
  * This macro can be used when you need to provide custom logic for setting
@@ -124,6 +124,6 @@ RCT_REMAP_VIEW_PROPERTY(name, __custom__, type)         \
  * This macro is used to map properties to the shadow view, instead of the view.
  */
 #define RCT_EXPORT_SHADOW_PROPERTY(name, type) \
-+ (NSArray *)propConfigShadow_##name { return @[@#type]; }
++ (NSArray<NSString *> *)propConfigShadow_##name { return @[@#type]; }
 
 @end

React/Views/RCTViewManager.m

@@ -69,7 +69,7 @@ RCT_EXPORT_MODULE()
   return [RCTShadowView new];
 }
 
-- (NSArray *)customBubblingEventTypes
+- (NSArray<NSString *> *)customBubblingEventTypes
 {
   return @[
 
@@ -90,7 +90,7 @@ RCT_EXPORT_MODULE()
   ];
 }
 
-- (NSArray *)customDirectEventTypes
+- (NSArray<NSString *> *)customDirectEventTypes
 {
   return @[];
 }

React/Views/UIView+React.h

@@ -15,6 +15,9 @@
 
 @interface UIView (React) <RCTComponent>
 
+- (NSArray<UIView<RCTComponent> *> *)reactSubviews;
+- (UIView<RCTComponent> *)reactSuperview;
+
 /**
  * Used by the UIIManager to set the view frame.
  * May be overriden to disable animation, etc.

React/Views/UIView+React.m

@@ -51,12 +51,12 @@
   [subview removeFromSuperview];
 }
 
-- (NSArray *)reactSubviews
+- (NSArray<UIView<RCTComponent> *> *)reactSubviews
 {
   return self.subviews;
 }
 
-- (UIView *)reactSuperview
+- (UIView<RCTComponent> *)reactSuperview
 {
   return self.superview;
 }