Use __typeof(self) when assigning weak reference for block.

Signed-off-by: 庞博 <bopang@sohu-inc.com>

@@ -45,7 +45,7 @@ static char imageURLKey;
     self.image = placeholder;
 
     if (url) {
-        __weak MKAnnotationView *wself = self;
+        __weak __typeof(self)wself = self;
         id <SDWebImageOperation> operation = [SDWebImageManager.sharedManager downloadImageWithURL:url options:options progress:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
             if (!wself) return;
             dispatch_main_sync_safe(^{

@@ -113,7 +113,7 @@ static NSString *const kCompletedCallbackKey = @"completed";
 
 - (id <SDWebImageOperation>)downloadImageWithURL:(NSURL *)url options:(SDWebImageDownloaderOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageDownloaderCompletedBlock)completedBlock {
     __block SDWebImageDownloaderOperation *operation;
-    __weak SDWebImageDownloader *wself = self;
+    __weak __typeof(self)wself = self;
 
     [self addProgressCallback:progressBlock andCompletedBlock:completedBlock forURL:url createCallback:^{
         NSTimeInterval timeoutInterval = wself.downloadTimeout;

@@ -68,7 +68,7 @@ static char imageURLStorageKey;
     
     self.imageURLStorage[@(state)] = url;
 
-    __weak UIButton *wself = self;
+    __weak __typeof(self)wself = self;
     id <SDWebImageOperation> operation = [SDWebImageManager.sharedManager downloadImageWithURL:url options:options progress:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
         if (!wself) return;
         dispatch_main_sync_safe(^{
@@ -111,7 +111,7 @@ static char imageURLStorageKey;
     [self setBackgroundImage:placeholder forState:state];
 
     if (url) {
-        __weak UIButton *wself = self;
+        __weak __typeof(self)wself = self;
         id <SDWebImageOperation> operation = [SDWebImageManager.sharedManager downloadImageWithURL:url options:options progress:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
             if (!wself) return;
             dispatch_main_sync_safe(^{

@@ -33,7 +33,7 @@
     [self sd_cancelCurrentHighlightedImageLoad];
 
     if (url) {
-        __weak UIImageView      *wself    = self;
+        __weak __typeof(self)wself = self;
         id<SDWebImageOperation> operation = [SDWebImageManager.sharedManager downloadImageWithURL:url options:options progress:progressBlock completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
             if (!wself) return;
             dispatch_main_sync_safe (^

@@ -49,7 +49,7 @@ static char imageURLKey;
     }
     
     if (url) {
-        __weak UIImageView *wself = self;
+        __weak __typeof(self)wself = self;
         id <SDWebImageOperation> operation = [SDWebImageManager.sharedManager downloadImageWithURL:url options:options progress:progressBlock completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
             if (!wself) return;
             dispatch_main_sync_safe(^{
@@ -92,7 +92,7 @@ static char imageURLKey;
 
 - (void)sd_setAnimationImagesWithURLs:(NSArray *)arrayOfURLs {
     [self sd_cancelCurrentAnimationImagesLoad];
-    __weak UIImageView *wself = self;
+    __weak __typeof(self)wself = self;
 
     NSMutableArray *operationsArray = [[NSMutableArray alloc] init];