Use NSOperation instead GCD, high level, supports cancel and add only if queue is empty (to avoid too frequent callback), don't need to create AutoReleasePool as well

Author: dreampiggy

Storage/FirebaseStorageUI/FUIStorageImageLoader.m

@@ -87,29 +87,28 @@ - (BOOL)canRequestImageForURL:(NSURL *)url {
  }
  // Download the image from Firebase Storage
  // Each download task use independent serial coder queue, to ensure callback in order during prorgessive decoding
- dispatch_queue_t coderQueue = dispatch_queue_create("com.google.firebaseui.storage.coderQueue", DISPATCH_QUEUE_SERIAL);
- FIRStorageDownloadTask * download = [storageRef dataWithMaxSize:size
- completion:^(NSData * _Nullable data, NSError * _Nullable error) {
- if (error) {
- dispatch_main_async_safe(^{
- if (completedBlock) {
- completedBlock(nil, nil, error, YES);
- }
- });
- return;
- }
- // Decode the image with data
- dispatch_async(coderQueue, ^{
- @autoreleasepool {
- UIImage *image = SDImageLoaderDecodeImageData(data, url, options, context);
- dispatch_main_async_safe(^{
- if (completedBlock) {
- completedBlock(image, data, nil, YES);
- }
- });
- }
- });
- }];
+ NSOperationQueue *coderQueue = [NSOperationQueue new];
+ coderQueue.maxConcurrentOperationCount = 1;
+ FIRStorageDownloadTask * download = [storageRef dataWithMaxSize:size completion:^(NSData * _Nullable data, NSError * _Nullable error) {
+ if (error) {
+ dispatch_main_async_safe(^{
+ if (completedBlock) {
+ completedBlock(nil, nil, error, YES);
+ }
+ });
+ return;
+ }
+ // Decode the image with data
+ [coderQueue cancelAllOperations];
+ [coderQueue addOperationWithBlock:^{
+ UIImage *image = SDImageLoaderDecodeImageData(data, url, options, context);
+ dispatch_main_async_safe(^{
+ if (completedBlock) {
+ completedBlock(image, data, nil, YES);
+ }
+ });
+ }];
+ }];
  // Observe the progress changes
  [download observeStatus:FIRStorageTaskStatusProgress handler:^(FIRStorageTaskSnapshot * _Nonnull snapshot) {
  // Check progressive decoding if need
@@ -128,8 +127,8 @@ - (BOOL)canRequestImageForURL:(NSURL *)url {
  // Get the finish status
  BOOL finished = receivedSize >= expectedSize;
  // This progress block may be called on main queue or global queue (depends configuration), always dispatched on coder queue
- dispatch_async(coderQueue, ^{
- @autoreleasepool {
+ if (coderQueue.operationCount == 0) {
+ [coderQueue addOperationWithBlock:^{
  UIImage *image = SDImageLoaderDecodeProgressiveImageData(partialData, url, finished, task, options, context);
  if (image) {
  dispatch_main_async_safe(^{
@@ -138,8 +137,8 @@ - (BOOL)canRequestImageForURL:(NSURL *)url {
  }
  });
  }
- }
- });
+ }];
+ }
  }
  }
  NSProgress *progress = snapshot.progress;