Move block before sending to the main queue

This can avoid some life cycle issue and increase performance

Author: dreampiggy

SDWebImage/Core/SDImageCache.m

@@ -40,12 +40,13 @@ - (void)cancel {
         }
         self.cancelled = YES;
 
-        dispatch_main_async_safe(^{
-            if (self.doneBlock) {
-                self.doneBlock(nil, nil, SDImageCacheTypeNone);
-                self.doneBlock = nil;
-            }
-        });
+        SDImageCacheQueryCompletionBlock doneBlock = self.doneBlock;
+        self.doneBlock = nil;
+        if (doneBlock) {
+            dispatch_main_async_safe(^{
+                doneBlock(nil, nil, SDImageCacheTypeNone);
+            });
+        }
     }
 }
 

SDWebImage/Core/SDWebImageDownloaderOperation.m

@@ -158,11 +158,11 @@ - (BOOL)cancel:(nullable id)token {
             [self.callbackTokens removeObjectIdenticalTo:token];
         }
         SDWebImageDownloaderCompletedBlock completedBlock = ((SDWebImageDownloaderOperationToken *)token).completedBlock;
-        dispatch_main_async_safe(^{
-            if (completedBlock) {
+        if (completedBlock) {
+            dispatch_main_async_safe(^{
                 completedBlock(nil, nil, [NSError errorWithDomain:SDWebImageErrorDomain code:SDWebImageErrorCancelled userInfo:@{NSLocalizedDescriptionKey : @"Operation cancelled by user during sending the request"}], YES);
-            }
-        });
+            });
+        }
     }
     return shouldCancel;
 }
@@ -697,11 +697,12 @@ - (void)callCompletionBlocksWithImage:(nullable UIImage *)image
         tokens = [self.callbackTokens copy];
     }
     for (SDWebImageDownloaderOperationToken *token in tokens) {
-        dispatch_main_async_safe(^{
-            if (token.completedBlock) {
-                token.completedBlock(image, imageData, error, finished);
-            }
-        });
+        SDWebImageDownloaderCompletedBlock completedBlock = token.completedBlock;
+        if (completedBlock) {
+            dispatch_main_async_safe(^{
+                completedBlock(image, imageData, error, finished);
+            });
+        }
     }
 }
 
@@ -710,11 +711,12 @@ - (void)callCompletionBlockWithToken:(nonnull SDWebImageDownloaderOperationToken
                            imageData:(nullable NSData *)imageData
                                error:(nullable NSError *)error
                             finished:(BOOL)finished {
-    dispatch_main_async_safe(^{
-        if (token.completedBlock) {
-            token.completedBlock(image, imageData, error, finished);
-        }
-    });
+    SDWebImageDownloaderCompletedBlock completedBlock = token.completedBlock;
+    if (completedBlock) {
+        dispatch_main_async_safe(^{
+            completedBlock(image, imageData, error, finished);
+        });
+    }
 }
 
 @end

SDWebImage/Core/SDWebImageManager.m

@@ -672,11 +672,11 @@ - (void)callCompletionBlockForOperation:(nullable SDWebImageCombinedOperation*)o
                               cacheType:(SDImageCacheType)cacheType
                                finished:(BOOL)finished
                                     url:(nullable NSURL *)url {
-    dispatch_main_async_safe(^{
-        if (completionBlock) {
+    if (completionBlock) {
+        dispatch_main_async_safe(^{
             completionBlock(image, data, error, cacheType, finished, url);
-        }
-    });
+        });
+    }
 }
 
 - (BOOL)shouldBlockFailedURLWithURL:(nonnull NSURL *)url

SDWebImage/Core/UIView+WebCache.m

@@ -229,12 +229,12 @@ - (void)setSd_imageProgress:(NSProgress *)sd_imageProgress {
 #if SD_UIKIT || SD_MAC
         [self sd_stopImageIndicator];
 #endif
-        dispatch_main_async_safe(^{
-            if (completedBlock) {
+        if (completedBlock) {
+            dispatch_main_async_safe(^{
                 NSError *error = [NSError errorWithDomain:SDWebImageErrorDomain code:SDWebImageErrorInvalidURL userInfo:@{NSLocalizedDescriptionKey : @"Image url is nil"}];
                 completedBlock(nil, nil, error, SDImageCacheTypeNone, YES, url);
-            }
-        });
+            });
+        }
     }
 
     return operation;