[React Native] Update image downloader

Summary:
Change `RCTImageDownloader` so it stores the `RCTDownloadTaskWrapper` for reuse. Modify `RCTDownloadTaskWrapper` to use associated objects to store the completion/progress blocks.

Libraries/Image/RCTDownloadTaskWrapper.h

@@ -14,13 +14,8 @@ typedef void (^RCTDataProgressBlock)(int64_t written, int64_t total);
 
 @interface RCTDownloadTaskWrapper : NSObject <NSURLSessionDownloadDelegate>
 
-@property (copy, nonatomic) RCTDataCompletionBlock completionBlock;
-@property (copy, nonatomic) RCTDataProgressBlock progressBlock;
-
 - (instancetype)initWithSessionConfiguration:(NSURLSessionConfiguration *)configuration delegateQueue:(NSOperationQueue *)delegateQueue;
 
 - (NSURLSessionDownloadTask *)downloadData:(NSURL *)url progressBlock:(RCTDataProgressBlock)progressBlock completionBlock:(RCTDataCompletionBlock)completionBlock;
 
-@property (nonatomic, assign) id<NSURLSessionDownloadDelegate> delegate;
-
 @end

Libraries/Image/RCTDownloadTaskWrapper.m

@@ -10,6 +10,42 @@
 
 #import "RCTDownloadTaskWrapper.h"
 
+#import <objc/runtime.h>
+
+static void *const RCTDownloadTaskWrapperCompletionBlockKey = (void *)&RCTDownloadTaskWrapperCompletionBlockKey;
+static void *const RCTDownloadTaskWrapperProgressBlockKey = (void *)&RCTDownloadTaskWrapperProgressBlockKey;
+
+@interface NSURLSessionTask (RCTDownloadTaskWrapper)
+
+@property (nonatomic, copy, setter=rct_setCompletionBlock:) RCTDataCompletionBlock rct_completionBlock;
+@property (nonatomic, copy, setter=rct_setProgressBlock:) RCTDataProgressBlock rct_progressBlock;
+
+@end
+
+@implementation NSURLSessionTask (RCTDownloadTaskWrapper)
+
+- (RCTDataCompletionBlock)rct_completionBlock
+{
+  return objc_getAssociatedObject(self, RCTDownloadTaskWrapperCompletionBlockKey);
+}
+
+- (void)rct_setCompletionBlock:(RCTDataCompletionBlock)completionBlock
+{
+  objc_setAssociatedObject(self, RCTDownloadTaskWrapperCompletionBlockKey, completionBlock, OBJC_ASSOCIATION_COPY_NONATOMIC);
+}
+
+- (RCTDataProgressBlock)rct_progressBlock
+{
+  return objc_getAssociatedObject(self, RCTDownloadTaskWrapperProgressBlockKey);
+}
+
+- (void)rct_setProgressBlock:(RCTDataProgressBlock)progressBlock
+{
+  objc_setAssociatedObject(self, RCTDownloadTaskWrapperProgressBlockKey, progressBlock, OBJC_ASSOCIATION_COPY_NONATOMIC);
+}
+
+@end
+
 @implementation RCTDownloadTaskWrapper
 {
   NSURLSession *_URLSession;
@@ -26,10 +62,10 @@
 
 - (NSURLSessionDownloadTask *)downloadData:(NSURL *)url progressBlock:(RCTDataProgressBlock)progressBlock completionBlock:(RCTDataCompletionBlock)completionBlock
 {
-  self.completionBlock = completionBlock;
-  self.progressBlock = progressBlock;
-
   NSURLSessionDownloadTask *task = [_URLSession downloadTaskWithURL:url completionHandler:nil];
+  task.rct_completionBlock = completionBlock;
+  task.rct_progressBlock = progressBlock;
+
   [task resume];
   return task;
 }
@@ -38,30 +74,28 @@
 
 - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
 {
-  if (self.completionBlock) {
+  if (downloadTask.rct_completionBlock) {
     NSData *data = [NSData dataWithContentsOfURL:location];
     dispatch_async(dispatch_get_main_queue(), ^{
-      self.completionBlock(downloadTask.response, data, nil);
+      downloadTask.rct_completionBlock(downloadTask.response, data, nil);
     });
   }
 }
 
 - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)didWriteData totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite;
 {
-  dispatch_async(dispatch_get_main_queue(), ^{
+  if (downloadTask.rct_progressBlock) {
-    if (self.progressBlock != nil) {
+    dispatch_async(dispatch_get_main_queue(), ^{
-      self.progressBlock(totalBytesWritten, totalBytesExpectedToWrite);
+      downloadTask.rct_progressBlock(totalBytesWritten, totalBytesExpectedToWrite);
-    }
+    });
-  });
+  }
 }
 
-- (void)URLSession:(NSURLSession *)session
+- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
-              task:(NSURLSessionTask *)task
-didCompleteWithError:(NSError *)error
 {
-  if (error && self.completionBlock) {
+  if (error && task.rct_completionBlock) {
     dispatch_async(dispatch_get_main_queue(), ^{
-      self.completionBlock(NULL, NULL, error);
+      task.rct_completionBlock(nil, nil, error);
     });
   }
 }

Libraries/Image/RCTImageDownloader.h

@@ -13,6 +13,7 @@
 
 typedef void (^RCTDataDownloadBlock)(NSData *data, NSError *error);
 typedef void (^RCTImageDownloadBlock)(UIImage *image, NSError *error);
+typedef void (^RCTImageDownloadCancellationBlock)(void);
 
 @interface RCTImageDownloader : NSObject
 
@@ -23,9 +24,9 @@ typedef void (^RCTImageDownloadBlock)(UIImage *image, NSError *error);
  * will not be executed on the same thread you called the method from, nor on
  * the main thread. Returns a token that can be used to cancel the download.
  */
-- (id)downloadDataForURL:(NSURL *)url
+- (RCTImageDownloadCancellationBlock)downloadDataForURL:(NSURL *)url
-           progressBlock:(RCTDataProgressBlock)progressBlock
+                                          progressBlock:(RCTDataProgressBlock)progressBlock
-                   block:(RCTDataDownloadBlock)block;
+                                                  block:(RCTDataDownloadBlock)block;
 
 /**
  * Downloads an image and decompresses it a the size specified. The compressed
@@ -33,19 +34,19 @@ typedef void (^RCTImageDownloadBlock)(UIImage *image, NSError *error);
  * will not be executed on the same thread you called the method from, nor on
  * the main thread. Returns a token that can be used to cancel the download.
  */
-- (id)downloadImageForURL:(NSURL *)url
+- (RCTImageDownloadCancellationBlock)downloadImageForURL:(NSURL *)url
-                     size:(CGSize)size
+                                                    size:(CGSize)size
-                    scale:(CGFloat)scale
+                                                   scale:(CGFloat)scale
-               resizeMode:(UIViewContentMode)resizeMode
+                                              resizeMode:(UIViewContentMode)resizeMode
-          backgroundColor:(UIColor *)backgroundColor
+                                         backgroundColor:(UIColor *)backgroundColor
-            progressBlock:(RCTDataProgressBlock)progressBlock
+                                           progressBlock:(RCTDataProgressBlock)progressBlock
-                    block:(RCTImageDownloadBlock)block;
+                                                   block:(RCTImageDownloadBlock)block;
 
 /**
  * Cancel an in-flight download. If multiple requets have been made for the
  * same image, only the request that relates to the token passed will be
  * cancelled.
  */
-- (void)cancelDownload:(id)downloadToken;
+- (void)cancelDownload:(RCTImageDownloadCancellationBlock)downloadToken;
 
 @end

Libraries/Image/RCTImageDownloader.m

@@ -23,6 +23,7 @@ CGRect RCTClipRect(CGSize, CGFloat, CGSize, CGFloat, UIViewContentMode);
   NSURLCache *_cache;
   dispatch_queue_t _processingQueue;
   NSMutableDictionary *_pendingBlocks;
+  RCTDownloadTaskWrapper *_downloadTaskWrapper;
 }
 
 + (RCTImageDownloader *)sharedInstance
@@ -41,22 +42,22 @@ CGRect RCTClipRect(CGSize, CGFloat, CGSize, CGFloat, UIViewContentMode);
     _cache = [[NSURLCache alloc] initWithMemoryCapacity:5 * 1024 * 1024 diskCapacity:200 * 1024 * 1024 diskPath:@"React/RCTImageDownloader"];
     _processingQueue = dispatch_queue_create("com.facebook.React.DownloadProcessingQueue", DISPATCH_QUEUE_SERIAL);
     _pendingBlocks = [[NSMutableDictionary alloc] init];
+
+    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
+    _downloadTaskWrapper = [[RCTDownloadTaskWrapper alloc] initWithSessionConfiguration:config delegateQueue:nil];
   }
 
   return self;
 }
 
-- (id)_downloadDataForURL:(NSURL *)url progressBlock:progressBlock block:(RCTCachedDataDownloadBlock)block
+- (RCTImageDownloadCancellationBlock)_downloadDataForURL:(NSURL *)url progressBlock:progressBlock block:(RCTCachedDataDownloadBlock)block
 {
-  NSString *cacheKey = url.absoluteString;
+  NSString *const cacheKey = url.absoluteString;
 
   __block BOOL cancelled = NO;
   __block NSURLSessionDownloadTask *task = nil;
 
-  NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
+  RCTImageDownloadCancellationBlock cancel = ^{
-  RCTDownloadTaskWrapper *downloadTaskWrapper = [[RCTDownloadTaskWrapper alloc] initWithSessionConfiguration:config delegateQueue:nil];
-
-  dispatch_block_t cancel = ^{
     cancelled = YES;
 
     dispatch_async(_processingQueue, ^{
@@ -90,7 +91,7 @@ CGRect RCTClipRect(CGSize, CGFloat, CGSize, CGFloat, UIViewContentMode);
       };
 
       NSURLRequest *request = [NSURLRequest requestWithURL:url];
-      task = [downloadTaskWrapper downloadData:url progressBlock:progressBlock completionBlock:^(NSURLResponse *response, NSData *data, NSError *error) {
+      task = [_downloadTaskWrapper downloadData:url progressBlock:progressBlock completionBlock:^(NSURLResponse *response, NSData *data, NSError *error) {
         if (!cancelled) {
           runBlocks(NO, data, error);
         }
@@ -120,20 +121,20 @@ CGRect RCTClipRect(CGSize, CGFloat, CGSize, CGFloat, UIViewContentMode);
   return [cancel copy];
 }
 
-- (id)downloadDataForURL:(NSURL *)url progressBlock:(RCTDataProgressBlock)progressBlock block:(RCTDataDownloadBlock)block
+- (RCTImageDownloadCancellationBlock)downloadDataForURL:(NSURL *)url progressBlock:(RCTDataProgressBlock)progressBlock block:(RCTDataDownloadBlock)block
 {
   return [self _downloadDataForURL:url progressBlock:progressBlock block:^(BOOL cached, NSData *data, NSError *error) {
     block(data, error);
   }];
 }
 
-- (id)downloadImageForURL:(NSURL *)url
+- (RCTImageDownloadCancellationBlock)downloadImageForURL:(NSURL *)url
-                     size:(CGSize)size
+                                                    size:(CGSize)size
-                    scale:(CGFloat)scale
+                                                   scale:(CGFloat)scale
-               resizeMode:(UIViewContentMode)resizeMode
+                                              resizeMode:(UIViewContentMode)resizeMode
-          backgroundColor:(UIColor *)backgroundColor
+                                         backgroundColor:(UIColor *)backgroundColor
-            progressBlock:(RCTDataProgressBlock)progressBlock
+                                           progressBlock:(RCTDataProgressBlock)progressBlock
-                    block:(RCTImageDownloadBlock)block
+                                                   block:(RCTImageDownloadBlock)block
 {
   return [self downloadDataForURL:url progressBlock:progressBlock block:^(NSData *data, NSError *error) {
     if (!data || error) {
@@ -182,10 +183,10 @@ CGRect RCTClipRect(CGSize, CGFloat, CGSize, CGFloat, UIViewContentMode);
   }];
 }
 
-- (void)cancelDownload:(id)downloadToken
+- (void)cancelDownload:(RCTImageDownloadCancellationBlock)downloadToken
 {
   if (downloadToken) {
-    ((dispatch_block_t)downloadToken)();
+    downloadToken();
   }
 }