Introducing RCTComponentViewFactory

Summary:
The whole mounting iOS infra now uses `ComponentHandle` instead of `std::string` as a reference to particular `ComponentView` implementation. All changes are pretty straightforward, we use a different thing/type to refer to the particular class; no changes in the logic besides a new `RCTComponentViewFactory` that serves the same role of classes registry as Objective-C runtime served previously.
That has several benefits:
* It should be slightly faster, mostly because we don't need to convert `char *` strings to `std::string` and then to `NSString *`.
* We don't need string-based component-name maps anymore (at least on this layer). We can call classes as we want and it will work because of classes are now explicit about which ShadowNodes they are compatible with.
* Most importantly, it's explicit now! That means that no runtime magic is involved anymore and we can rely on static linting tool now and not be afraid of improper code stripping/overoptimization.

Reviewed By: mdvacca

Differential Revision: D13130760

fbshipit-source-id: aadf70525a1335b96992443abae4da359efdc829

React/Fabric/Mounting/MountItems/RCTCreateMountItem.h

@@ -7,6 +7,7 @@
 
 #import <UIKit/UIKit.h>
 
+#import <react/core/ReactPrimitives.h>
 #import <React/RCTMountItemProtocol.h>
 #import <React/RCTPrimitives.h>
 
@@ -19,8 +20,8 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @interface RCTCreateMountItem : NSObject <RCTMountItemProtocol>
 
-- (instancetype)initWithComponentName:(NSString *)componentName
-                                  tag:(ReactTag)tag;
+- (instancetype)initWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+                                    tag:(ReactTag)tag;
 
 @end
 

React/Fabric/Mounting/MountItems/RCTCreateMountItem.mm

@@ -9,16 +9,18 @@
 
 #import "RCTComponentViewRegistry.h"
 
+using namespace facebook::react;
+
 @implementation RCTCreateMountItem {
-  NSString *_componentName;
+  ComponentHandle _componentHandle;
   ReactTag _tag;
 }
 
-- (instancetype)initWithComponentName:(NSString *)componentName
-                                  tag:(ReactTag)tag
+- (instancetype)initWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+                                    tag:(ReactTag)tag
 {
   if (self = [super init]) {
-    _componentName = componentName;
+    _componentHandle = componentHandle;
     _tag = tag;
   }
 
@@ -27,7 +29,7 @@
 
 - (void)executeWithRegistry:(RCTComponentViewRegistry *)registry
 {
-  [registry dequeueComponentViewWithName:_componentName tag:_tag];
+  [registry dequeueComponentViewWithComponentHandle:_componentHandle tag:_tag];
 }
 
 @end

React/Fabric/Mounting/MountItems/RCTDeleteMountItem.h

@@ -7,6 +7,7 @@
 
 #import <UIKit/UIKit.h>
 
+#import <react/core/ReactPrimitives.h>
 #import <React/RCTMountItemProtocol.h>
 #import <React/RCTPrimitives.h>
 
@@ -17,8 +18,8 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @interface RCTDeleteMountItem : NSObject <RCTMountItemProtocol>
 
-- (instancetype)initWithComponentName:(NSString *)componentName
-                                  tag:(ReactTag)tag;
+- (instancetype)initWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+                                    tag:(ReactTag)tag;
 
 @end
 

React/Fabric/Mounting/MountItems/RCTDeleteMountItem.mm

@@ -9,16 +9,18 @@
 
 #import "RCTComponentViewRegistry.h"
 
+using namespace facebook::react;
+
 @implementation RCTDeleteMountItem {
-  NSString *_componentName;
+  ComponentHandle _componentHandle;
   ReactTag _tag;
 }
 
-- (instancetype)initWithComponentName:(NSString *)componentName
-                                  tag:(ReactTag)tag
+- (instancetype)initWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+                                    tag:(ReactTag)tag
 {
   if (self = [super init]) {
-    _componentName = componentName;
+    _componentHandle = componentHandle;
     _tag = tag;
   }
 
@@ -33,7 +35,7 @@
     return;
   }
 
-  [registry enqueueComponentViewWithName:_componentName tag:_tag componentView:componentView];
+  [registry enqueueComponentViewWithComponentHandle:_componentHandle tag:_tag componentView:componentView];
 }
 
 @end

React/Fabric/Mounting/RCTComponentViewFactory.h

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <UIKit/UIKit.h>
+
+#import <React/RCTComponentViewProtocol.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * Registry of supported component view classes that can instantiate
+ * view component instances by given component handle.
+ */
+@interface RCTComponentViewFactory : NSObject
+
+/**
+ * Constructs and returns an instance of the class with a bunch of already registered standard components.
+ */
++ (RCTComponentViewFactory *)standardComponentViewFactory;
+
+/**
+ * Registers a component view class in the factory.
+ */
+- (void)registerComponentViewClass:(Class<RCTComponentViewProtocol>)componentViewClass;
+
+/**
+ * Creates a component view with given component handle.
+ */
+- (UIView<RCTComponentViewProtocol> *)createComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle;
+
+@end
+
+NS_ASSUME_NONNULL_END

React/Fabric/Mounting/RCTComponentViewFactory.mm

@@ -0,0 +1,65 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import "RCTComponentViewFactory.h"
+
+#import <React/RCTAssert.h>
+#import <react/core/ReactPrimitives.h>
+
+#import "RCTViewComponentView.h"
+#import "RCTImageComponentView.h"
+#import "RCTScrollViewComponentView.h"
+#import "RCTParagraphComponentView.h"
+#import "RCTRootComponentView.h"
+#import "RCTActivityIndicatorViewComponentView.h"
+#import "RCTSwitchComponentView.h"
+
+using namespace facebook::react;
+
+@implementation RCTComponentViewFactory
+{
+  std::unordered_map<ComponentHandle, Class<RCTComponentViewProtocol>> _registry;
+}
+
++ (RCTComponentViewFactory *)standardComponentViewFactory
+{
+  RCTAssertMainQueue();
+
+  RCTComponentViewFactory *componentViewFactory = [[RCTComponentViewFactory alloc] init];
+
+  [componentViewFactory registerComponentViewClass:[RCTViewComponentView class]];
+  [componentViewFactory registerComponentViewClass:[RCTRootComponentView class]];
+  [componentViewFactory registerComponentViewClass:[RCTScrollViewComponentView class]];
+  [componentViewFactory registerComponentViewClass:[RCTImageComponentView class]];
+  [componentViewFactory registerComponentViewClass:[RCTParagraphComponentView class]];
+  [componentViewFactory registerComponentViewClass:[RCTActivityIndicatorViewComponentView class]];
+  [componentViewFactory registerComponentViewClass:[RCTSwitchComponentView class]];
+
+  return componentViewFactory;
+}
+
+- (void)registerComponentViewClass:(Class<RCTComponentViewProtocol>)componentViewClass
+{
+  RCTAssertMainQueue();
+
+  ComponentHandle componentHandle = [componentViewClass componentHandle];
+  _registry[componentHandle] = componentViewClass;
+}
+
+- (UIView<RCTComponentViewProtocol> *)createComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+{
+  RCTAssertMainQueue();
+
+  auto iterator = _registry.find(componentHandle);
+  RCTAssert(
+    iterator != _registry.end(),
+    @"ComponentView with componentHandle `%lli` (`%s`) not found.", componentHandle, (char *)componentHandle);
+  Class componentViewClass = iterator->second;
+  return [[componentViewClass alloc] init];
+}
+
+@end

React/Fabric/Mounting/RCTComponentViewRegistry.h

@@ -7,6 +7,8 @@
 
 #import <UIKit/UIKit.h>
 
+#import <react/core/ReactPrimitives.h>
+#import <React/RCTComponentViewFactory.h>
 #import <React/RCTComponentViewProtocol.h>
 
 NS_ASSUME_NONNULL_BEGIN
@@ -17,21 +19,23 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @interface RCTComponentViewRegistry : NSObject
 
+@property (nonatomic, strong, readonly) RCTComponentViewFactory *componentViewFactory;
+
 /**
  * Returns a native view instance from the recycle pool (or create)
- * for given `componentName` and with given `tag`.
+ * for given `componentHandle` and with given `tag`.
  * #RefuseSingleUse
  */
-- (UIView<RCTComponentViewProtocol> *)dequeueComponentViewWithName:(NSString *)componentName
-                                                               tag:(ReactTag)tag;
+- (UIView<RCTComponentViewProtocol> *)dequeueComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+                                                                          tag:(ReactTag)tag;
 
 /**
  * Puts a given native component view to the recycle pool.
  * #RefuseSingleUse
  */
-- (void)enqueueComponentViewWithName:(NSString *)componentName
-                                 tag:(ReactTag)tag
-                       componentView:(UIView<RCTComponentViewProtocol> *)componentView;
+- (void)enqueueComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle
+                                            tag:(ReactTag)tag
+                                  componentView:(UIView<RCTComponentViewProtocol> *)componentView;
 
 /**
  * Returns a native component view by given `tag`.
@@ -46,7 +50,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * Creates a component view with a given type and puts it to the recycle pool.
  */
-- (void)preliminaryCreateComponentViewWithName:(NSString *)componentName;
+- (void)optimisticallyCreateComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle;
 
 @end
 

React/Fabric/Mounting/RCTComponentViewRegistry.mm

@@ -10,6 +10,8 @@
 #import <Foundation/NSMapTable.h>
 #import <React/RCTAssert.h>
 
+using namespace facebook::react;
+
 #define LEGACY_UIMANAGER_INTEGRATION_ENABLED 1
 
 #ifdef LEGACY_UIMANAGER_INTEGRATION_ENABLED
@@ -67,8 +69,8 @@
 const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
 
 @implementation RCTComponentViewRegistry {
-  NSMapTable<id, UIView<RCTComponentViewProtocol> *> *_registry;
-  NSMapTable<NSString *, NSHashTable<UIView<RCTComponentViewProtocol> *> *> *_recyclePool;
+  NSMapTable<id /* ReactTag */, UIView<RCTComponentViewProtocol> *> *_registry;
+  NSMapTable<id /* ComponentHandle */, NSHashTable<UIView<RCTComponentViewProtocol> *> *> *_recyclePool;
 }
 
 - (instancetype)init
@@ -76,15 +78,16 @@ const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
   if (self = [super init]) {
     _registry = [NSMapTable mapTableWithKeyOptions:NSPointerFunctionsIntegerPersonality | NSPointerFunctionsOpaqueMemory
                                       valueOptions:NSPointerFunctionsObjectPersonality];
-    _recyclePool = [NSMapTable mapTableWithKeyOptions:NSPointerFunctionsObjectPersonality
+    _recyclePool = [NSMapTable mapTableWithKeyOptions:NSPointerFunctionsOpaquePersonality | NSPointerFunctionsOpaqueMemory
                                          valueOptions:NSPointerFunctionsObjectPersonality];
+    _componentViewFactory = [RCTComponentViewFactory standardComponentViewFactory];
   }
 
   return self;
 }
 
-- (UIView<RCTComponentViewProtocol> *)dequeueComponentViewWithName:(NSString *)componentName
-                                                               tag:(ReactTag)tag
+- (UIView<RCTComponentViewProtocol> *)dequeueComponentViewWithComponentHandle:(ComponentHandle)componentHandle
+                                                                          tag:(ReactTag)tag
 {
   RCTAssertMainQueue();
 
@@ -92,7 +95,7 @@ const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
     @"RCTComponentViewRegistry: Attempt to dequeue already registered component.");
 
   UIView<RCTComponentViewProtocol> *componentView =
-    [self _dequeueComponentViewWithName:componentName];
+    [self _dequeueComponentViewWithComponentHandle:componentHandle];
   componentView.tag = tag;
   [_registry setObject:componentView forKey:(__bridge id)(void *)tag];
 
@@ -103,9 +106,9 @@ const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
   return componentView;
 }
 
-- (void)enqueueComponentViewWithName:(NSString *)componentName
-                                 tag:(ReactTag)tag
-                       componentView:(UIView<RCTComponentViewProtocol> *)componentView
+- (void)enqueueComponentViewWithComponentHandle:(ComponentHandle)componentHandle
+                                            tag:(ReactTag)tag
+                                  componentView:(UIView<RCTComponentViewProtocol> *)componentView
 {
   RCTAssertMainQueue();
 
@@ -118,14 +121,14 @@ const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
 
   [_registry removeObjectForKey:(__bridge id)(void *)tag];
   componentView.tag = 0;
-  [self _enqueueComponentViewWithName:componentName componentView:componentView];
+  [self _enqueueComponentViewWithComponentHandle:componentHandle componentView:componentView];
 }
 
-- (void)preliminaryCreateComponentViewWithName:(NSString *)componentName
+- (void)optimisticallyCreateComponentViewWithComponentHandle:(ComponentHandle)componentHandle
 {
   RCTAssertMainQueue();
-  [self _enqueueComponentViewWithName:componentName
-                        componentView:[self _createComponentViewWithName:componentName]];
+  [self _enqueueComponentViewWithComponentHandle:componentHandle
+                                   componentView:[self.componentViewFactory createComponentViewWithComponentHandle:componentHandle]];
 }
 
 - (UIView<RCTComponentViewProtocol> *)componentViewByTag:(ReactTag)tag
@@ -140,21 +143,13 @@ const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
   return componentView.tag;
 }
 
-- (UIView<RCTComponentViewProtocol> *)_createComponentViewWithName:(NSString *)componentName
+- (nullable UIView<RCTComponentViewProtocol> *)_dequeueComponentViewWithComponentHandle:(ComponentHandle)componentHandle
 {
   RCTAssertMainQueue();
-  // This is temporary approach.
-  NSString *className = [NSString stringWithFormat:@"RCT%@ComponentView", componentName];
-  UIView<RCTComponentViewProtocol> *componentView = [[NSClassFromString(className) alloc] init];
-  return componentView;
-}
-
-- (nullable UIView<RCTComponentViewProtocol> *)_dequeueComponentViewWithName:(NSString *)componentName
-{
-  RCTAssertMainQueue();
-  NSHashTable<UIView<RCTComponentViewProtocol> *> *componentViews = [_recyclePool objectForKey:componentName];
+  NSHashTable<UIView<RCTComponentViewProtocol> *> *componentViews =
+    [_recyclePool objectForKey:(__bridge id)(void *)componentHandle];
   if (!componentViews || componentViews.count == 0) {
-    return [self _createComponentViewWithName:componentName];
+    return [self.componentViewFactory createComponentViewWithComponentHandle:componentHandle];
   }
 
   UIView<RCTComponentViewProtocol> *componentView = [componentViews anyObject];
@@ -162,16 +157,17 @@ const NSInteger RCTComponentViewRegistryRecyclePoolMaxSize = 1024;
   return componentView;
 }
 
-- (void)_enqueueComponentViewWithName:(NSString *)componentName
-                        componentView:(UIView<RCTComponentViewProtocol> *)componentView
+- (void)_enqueueComponentViewWithComponentHandle:(ComponentHandle)componentHandle
+                                   componentView:(UIView<RCTComponentViewProtocol> *)componentView
 {
   RCTAssertMainQueue();
   [componentView prepareForRecycle];
 
-  NSHashTable<UIView<RCTComponentViewProtocol> *> *componentViews = [_recyclePool objectForKey:componentName];
+  NSHashTable<UIView<RCTComponentViewProtocol> *> *componentViews =
+    [_recyclePool objectForKey:(__bridge id)(void *)componentHandle];
   if (!componentViews) {
     componentViews = [NSHashTable hashTableWithOptions:NSPointerFunctionsObjectPersonality];
-    [_recyclePool setObject:componentViews forKey:componentName];
+    [_recyclePool setObject:componentViews forKey:(__bridge id)(void *)componentHandle];
   }
 
   if (componentViews.count >= RCTComponentViewRegistryRecyclePoolMaxSize) {

React/Fabric/Mounting/RCTMountingManager.h

@@ -7,6 +7,7 @@
 
 #import <UIKit/UIKit.h>
 
+#import <react/core/ReactPrimitives.h>
 #import <react/uimanager/ShadowView.h>
 #import <react/uimanager/ShadowViewMutation.h>
 #import <React/RCTPrimitives.h>
@@ -37,7 +38,7 @@ NS_ASSUME_NONNULL_BEGIN
  * The receiver is free to ignore the request.
  * Can be called from any thread.
  */
-- (void)preliminaryCreateComponentViewWithName:(NSString *)componentName;
+- (void)optimisticallyCreateComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle;
 
 @end
 

React/Fabric/Mounting/RCTMountingManager.mm

@@ -47,19 +47,17 @@ using namespace facebook::react;
   for (const auto &mutation : mutations) {
     switch (mutation.type) {
       case ShadowViewMutation::Create: {
-        NSString *componentName = RCTNSStringFromString(mutation.newChildShadowView.componentName, NSASCIIStringEncoding);
         RCTCreateMountItem *mountItem =
-          [[RCTCreateMountItem alloc] initWithComponentName:componentName
-                                                        tag:mutation.newChildShadowView.tag];
+          [[RCTCreateMountItem alloc] initWithComponentHandle:mutation.newChildShadowView.componentHandle
+                                                          tag:mutation.newChildShadowView.tag];
         [mountItems addObject:mountItem];
         break;
       }
 
       case ShadowViewMutation::Delete: {
-        NSString *componentName = RCTNSStringFromString(mutation.oldChildShadowView.componentName, NSASCIIStringEncoding);
         RCTDeleteMountItem *mountItem =
-          [[RCTDeleteMountItem alloc] initWithComponentName:componentName
-                                                        tag:mutation.oldChildShadowView.tag];
+          [[RCTDeleteMountItem alloc] initWithComponentHandle:mutation.oldChildShadowView.componentHandle
+                                                          tag:mutation.oldChildShadowView.tag];
         [mountItems addObject:mountItem];
         break;
       }
@@ -170,10 +168,10 @@ using namespace facebook::react;
   [self.delegate mountingManager:self didMountComponentsWithRootTag:rootTag];
 }
 
-- (void)preliminaryCreateComponentViewWithName:(NSString *)componentName
+- (void)optimisticallyCreateComponentViewWithComponentHandle:(ComponentHandle)componentHandle
 {
   RCTExecuteOnMainQueue(^{
-    [self->_componentViewRegistry preliminaryCreateComponentViewWithName:componentName];
+    [self->_componentViewRegistry optimisticallyCreateComponentViewWithComponentHandle:componentHandle];
   });
 }
 

React/Fabric/RCTScheduler.h

@@ -25,7 +25,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)schedulerDidFinishTransaction:(facebook::react::ShadowViewMutationList)mutations
                               rootTag:(ReactTag)rootTag;
 
-- (void)schedulerDidRequestPreliminaryViewAllocationWithComponentName:(NSString *)componentName;
+- (void)schedulerOptimisticallyCreateComponentViewWithComponentHandle:(facebook::react::ComponentHandle)componentHandle;
 
 @end
 

React/Fabric/RCTScheduler.mm

@@ -29,7 +29,7 @@ public:
 
   void schedulerDidRequestPreliminaryViewAllocation(SurfaceId surfaceId, ComponentName componentName, bool isLayoutable, ComponentHandle componentHandle) override {
     RCTScheduler *scheduler = (__bridge RCTScheduler *)scheduler_;
-    [scheduler.delegate schedulerDidRequestPreliminaryViewAllocationWithComponentName:RCTNSStringFromString(componentName, NSASCIIStringEncoding)];
+    [scheduler.delegate schedulerOptimisticallyCreateComponentViewWithComponentHandle:componentHandle];
   }
 
 private:

React/Fabric/RCTSurfacePresenter.h

@@ -9,6 +9,7 @@
 #import <memory>
 
 #import <React/RCTBridge.h>
+#import <React/RCTComponentViewFactory.h>
 #import <React/RCTPrimitives.h>
 
 NS_ASSUME_NONNULL_BEGIN
@@ -26,6 +27,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (instancetype)initWithBridge:(RCTBridge *)bridge;
 
+@property (nonatomic, readonly) RCTComponentViewFactory *componentViewFactory;
+
 @end
 
 @interface RCTSurfacePresenter (Surface)

React/Fabric/RCTSurfacePresenter.mm

@@ -26,6 +26,7 @@
 #import <React/RCTUtils.h>
 #import <react/core/LayoutContext.h>
 #import <react/core/LayoutConstraints.h>
+#import <react/components/root/RootShadowNode.h>
 #import <react/imagemanager/ImageManager.h>
 #import <react/uimanager/ContextContainer.h>
 
@@ -80,6 +81,11 @@ using namespace facebook::react;
   [[NSNotificationCenter defaultCenter] removeObserver:self];
 }
 
+- (RCTComponentViewFactory *)componentViewFactory
+{
+  return _mountingManager.componentViewRegistry.componentViewFactory;
+}
+
 #pragma mark - Internal Surface-dedicated Interface
 
 - (void)registerSurface:(RCTFabricSurface *)surface
@@ -188,7 +194,8 @@ using namespace facebook::react;
 
 - (void)_startSurface:(RCTFabricSurface *)surface
 {
-  [_mountingManager.componentViewRegistry dequeueComponentViewWithName:@"Root" tag:surface.rootTag];
+  [_mountingManager.componentViewRegistry dequeueComponentViewWithComponentHandle:RootShadowNode::Handle()
+                                                                              tag:surface.rootTag];
 
   LayoutContext layoutContext = {
     .pointScaleFactor = RCTScreenScale()
@@ -210,8 +217,11 @@ using namespace facebook::react;
 {
   [self._scheduler stopSurfaceWithSurfaceId:surface.rootTag];
 
-  UIView<RCTComponentViewProtocol> *rootView = [_mountingManager.componentViewRegistry componentViewByTag:surface.rootTag];
-  [_mountingManager.componentViewRegistry enqueueComponentViewWithName:@"Root" tag:surface.rootTag componentView:rootView];
+  UIView<RCTComponentViewProtocol> *rootView =
+    [_mountingManager.componentViewRegistry componentViewByTag:surface.rootTag];
+  [_mountingManager.componentViewRegistry enqueueComponentViewWithComponentHandle:RootShadowNode::Handle()
+                                                                              tag:surface.rootTag
+                                                                    componentView:rootView];
 
   [surface _unsetStage:(RCTSurfaceStagePrepared | RCTSurfaceStageMounted)];
 }
@@ -243,9 +253,9 @@ using namespace facebook::react;
                                             rootTag:rootTag];
 }
 
-- (void)schedulerDidRequestPreliminaryViewAllocationWithComponentName:(NSString *)componentName
+- (void)schedulerOptimisticallyCreateComponentViewWithComponentHandle:(ComponentHandle)componentHandle
 {
-  [_mountingManager preliminaryCreateComponentViewWithName:componentName];
+  [_mountingManager optimisticallyCreateComponentViewWithComponentHandle:componentHandle];
 }
 
 #pragma mark - RCTMountingManagerDelegate