SDWebImageManager是SDWebImage的核心类。它拥有一个SDWebImageCache和一个SDWebImageDownloader属性，分别用于图片的缓存和下载处理。虽然是核心类，但它的源码很简单，这是因为相应的功能职责进行了良好的分类。下面我们来看一下它的源码。
1.SDWebImageOptions
typedef NS_OPTIONS(NSUInteger, SDWebImageOptions) { /** * By default, when a URL fail to be downloaded, the URL is blacklisted so the library won't keep trying. * This flag disable this blacklisting. */ //默认情况下，当一个URL下载失败的时候，这个URL会被加入黑名单列表，下次再有这个url的请求则停止请求。如果为true，这个值表示需要再尝试请求。 SDWebImageRetryFailed = 1 << 0, /** * By default, image downloads are started during UI interactions, this flags disable this feature, * leading to delayed download on UIScrollView deceleration for instance. */ //默认情况下，当UI可以交互的时候就开始加载图片。这个标记可以阻止这个时候加载。而是当UIScrollView开始减速滑动的时候开始加载。 SDWebImageLowPriority = 1 << 1, /** * This flag disables on-disk caching */ //这个属性禁止磁盘缓存 SDWebImageCacheMemoryOnly = 1 << 2, /** * This flag enables progressive download, the image is displayed progressively during download as a browser would do. * By default, the image is only displayed once completely downloaded. */ //这个标记允许图片在加载过程中显示，就像浏览器那样。默认情况下，图片只会在加载完成以后再显示。 SDWebImageProgressiveDownload = 1 << 3, /** * Even if the image is cached, respect the HTTP response cache control, and refresh the image from remote location if needed. * The disk caching will be handled by NSURLCache instead of SDWebImage leading to slight performance degradation. * This option helps deal with images changing behind the same request URL, e.g. Facebook graph api profile pics. * If a cached image is refreshed, the completion block is called once with the cached image and again with the final image. * * Use this flag only if you can't make your URLs static with embedded cache busting parameter. */ /* *即使本地已经缓存了图片，但是根据HTTP的缓存策略去网络上加载图片。也就是说本地缓存了也不管了，尝试从网络上加载数据。但是具体是从代理加载、HTTP缓存加载、还是原始服务器加载这个就根据HTTP的请求头配置。 *使用NSURLCache而不是SDWebImage来处理磁盘缓存。从而可能会导致轻微的性能损害。 *这个选项专门用于处理，url地址没有变，但是url对应的图片数据在服务器改变的情况。 *如果一个缓存图片更新了，则completion这个回调会被调用两次，一次返回缓存图片，一次返回最终图片。 *我们只有在不能确保URL和它对应的内容不能完全对应的时候才使用这个标记。 */ SDWebImageRefreshCached = 1 << 4, /** * In iOS 4+, continue the download of the image if the app goes to background. This is achieved by asking the system for * extra time in background to let the request finish. If the background task expires the operation will be cancelled. */ //当应用进入后台以后，图片继续下载。应用进入后台以后，通过向系统申请额外的时间来完成。如果时间超时，那么下载操作会被取消。 SDWebImageContinueInBackground = 1 << 5, /** * Handles cookies stored in NSHTTPCookieStore by setting * NSMutableURLRequest.HTTPShouldHandleCookies = YES; */ //处理缓存在`NSHTTPCookieStore`对象里面的cookie。通过设置`NSMutableURLRequest.HTTPShouldHandleCookies = YES`来实现的。 SDWebImageHandleCookies = 1 << 6, /** * Enable to allow untrusted SSL certificates. * Useful for testing purposes. Use with caution in production. */ //允许非信任的SSL证书请求。 //在测试的时候很有用。但是正式环境要小心使用。 SDWebImageAllowInvalidSSLCertificates = 1 << 7, /** * By default, images are loaded in the order in which they were queued. This flag moves them to * the front of the queue. */ //默认情况下，图片加载的顺序是根据加入队列的顺序加载的。但是这个标记会把任务加入队列的最前面。 SDWebImageHighPriority = 1 << 8, /** * By default, placeholder images are loaded while the image is loading. This flag will delay the loading * of the placeholder image until after the image has finished loading. */ //默认情况下，在图片加载的过程中，会显示占位图。 //但是这个标记会阻止显示占位图直到图片加载完成。 SDWebImageDelayPlaceholder = 1 << 9, /** * We usually don't call transformDownloadedImage delegate method on animated images, * as most transformation code would mangle it. * Use this flag to transform them anyway. */ //默认情况下，我们不会去调用`animated images`(估计就是多张图片循环显示或者GIF图片)的`transformDownloadedImage`代理方法来处理图片。因为大部分transformation操作会对图片做无用处理。 //用这个标记表示无论如何都要对图片做transform处理。 SDWebImageTransformAnimatedImage = 1 << 10, /** * By default, image is added to the imageView after download. But in some cases, we want to * have the hand before setting the image (apply a filter or add it with cross-fade animation for instance) * Use this flag if you want to manually set the image in the completion when success */ //默认情况下，图片在下载完成以后都会被自动加载到UIImageView对象上面。但是有时我们希望UIImageView加载我们手动处理以后的图片。 //这个标记允许我们在completion这个Block中手动设置处理好以后的图片。 SDWebImageAvoidAutoSetImage = 1 << 11, /** * By default, images are decoded respecting their original size. On iOS, this flag will scale down the * images to a size compatible with the constrained memory of devices. * If `SDWebImageProgressiveDownload` flag is set the scale down is deactivated. */ //默认情况下，图片会按照它的原始大小来解码显示。根据设备的内存限制，这个属性会调整图片的尺寸到合适的大小再解码。 //如果`SDWebImageProgressiveDownload`标记被设置了，则这个flag不起作用。 SDWebImageScaleDownLargeImages = 1 << 12 };
2.宏定义
/** 图片下载完成回调Block(外部使用，一般在我们常使用的视图分类方法中用) @param image 图片 @param error 错误信息 @param cacheType 图片获取方式(本地缓存;内存缓存;网络) @param imageURL 图片URL */ typedef void(^SDExternalCompletionBlock)(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL); /** 图片下载完成回调Block(内部使用，仅在本类中使用) @param image 图片，如果请求出错，那么image参数为nil @param data 图片数据 @param error 错误信息 @param cacheType 图片获取方式(本地缓存;内存缓存;网络) @param finished 是否下载完成 @param imageURL 图片URL */ typedef void(^SDInternalCompletionBlock)(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, SDImageCacheType cacheType, BOOL finished, NSURL * _Nullable imageURL); /** 对URL格式做处理，在方法cacheKeyForURL:中使用 @param url URL @return 处理之后的URL */ typedef NSString * _Nullable (^SDWebImageCacheKeyFilterBlock)(NSURL * _Nullable url);
3.协议SDWebImageManagerDelegate
@protocol SDWebImageManagerDelegate <NSObject> @optional /** 在缓存中没有找到图片，控制是否去下载图片 @param imageManager SDWebImageManager @param imageURL 图片URL @return YES/NO */ - (BOOL)imageManager:(nonnull SDWebImageManager *)imageManager shouldDownloadImageForURL:(nullable NSURL *)imageURL; /** 图片下载完成，在保存到磁盘和内存之前，对图片进行转换(主要是针对动态图) @param imageManager SDWebImageManager @param image 图片 @param imageURL 图片URL @return 转换之后的图片 */ - (nullable UIImage *)imageManager:(nonnull SDWebImageManager *)imageManager transformDownloadedImage:(nullable UIImage *)image withURL:(nullable NSURL *)imageURL; @end
4.SDWebImageCombinedOperation
SDWebImageCombinedOperation是对每一个下载任务的封装，它最重要的是提供了一个取消任务功能。
@interface SDWebImageCombinedOperation : NSObject <SDWebImageOperation> @property (assign, nonatomic, getter = isCancelled) BOOL cancelled; //!<用于判断Operation是否已经取消 @property (copy, nonatomic, nullable) SDWebImageNoParamsBlock cancelBlock; //!<取消回调的Block @property (strong, nonatomic, nullable) NSOperation *cacheOperation; //!<NSOperation对象。可以通过这个属性取消一个NSOperation @end @implementation SDWebImageCombinedOperation /** 取消Operation的回调Block @param cancelBlock 回调Block */ - (void)setCancelBlock:(nullable SDWebImageNoParamsBlock)cancelBlock { // check if the operation is already cancelled, then we just call the cancelBlock if (self.isCancelled) { if (cancelBlock) { cancelBlock(); } _cancelBlock = nil; // don't forget to nil the cancelBlock, otherwise we will get crashes } else { _cancelBlock = [cancelBlock copy]; } } /** 这个方法继承自`SDWebImageOperation`协议，方法里面会调用`SDWebImageDownlaoderOperation`或者`NSOperation`的cancel方法 */ - (void)cancel { self.cancelled = YES; if (self.cacheOperation) { //调用`SDWebImageDownlaoderOperation`或者`NSOperation`的cancel方法 [self.cacheOperation cancel]; self.cacheOperation = nil; } if (self.cancelBlock) { self.cancelBlock(); // TODO: this is a temporary fix to #809. // Until we can figure the exact cause of the crash, going with the ivar instead of the setter // self.cancelBlock = nil; _cancelBlock = nil; } } @end
5.SDWebImageManager的属性
//.h文件 @property (weak, nonatomic, nullable) id <SDWebImageManagerDelegate> delegate; //!<代理 @property (strong, nonatomic, readonly, nullable) SDImageCache *imageCache; //!<缓存对象 @property (strong, nonatomic, readonly, nullable) SDWebImageDownloader *imageDownloader; //!<下载对象 //.m文件 @property (strong, nonatomic, readwrite, nonnull) SDImageCache *imageCache; //!<重写为可读写的缓存对象 @property (strong, nonatomic, readwrite, nonnull) SDWebImageDownloader *imageDownloader; //!<重写为可读写的下载对象 @property (strong, nonatomic, nonnull) NSMutableSet<NSURL *> *failedURLs; //!<加载失败的URL @property (strong, nonatomic, nonnull) NSMutableArray<SDWebImageCombinedOperation *> *runningOperations; //!<当前正在加载的任务
6.SDWebImageManager的方法
6.1初始化
+ (nonnull instancetype)sharedManager { static dispatch_once_t once; static id instance; dispatch_once(&once, ^{ instance = [self new]; }); return instance; } - (nonnull instancetype)init { SDImageCache *cache = [SDImageCache sharedImageCache]; SDWebImageDownloader *downloader = [SDWebImageDownloader sharedDownloader]; return [self initWithCache:cache downloader:downloader]; } /** 初始化 @param cache SDImageCache对象 @param downloader SDWebImageDownloader对象 @return 返回初始化结果 */ - (nonnull instancetype)initWithCache:(nonnull SDImageCache *)cache downloader:(nonnull SDWebImageDownloader *)downloader { if ((self = [super init])) { _imageCache = cache; _imageDownloader = downloader; //用于保存加载失败的url集合 _failedURLs = [NSMutableSet new]; //用于保存当前正在加载的Operation _runningOperations = [NSMutableArray new]; } return self; }
6.2缓存查询
/** 根据url获取url对应的缓存key。如果有实现指定的url转换key的Block，则用这个方式转换为key；否则直接用url的绝对路径作为key @param url url @return 缓存的key */ - (nullable NSString *)cacheKeyForURL:(nullable NSURL *)url { if (!url) { return @""; } if (self.cacheKeyFilter) { return self.cacheKeyFilter(url); } else { return url.absoluteString; } } /** url的缓存是否存在 @param url 缓存数据对应的url @param completionBlock 缓存结果回调 */ - (void)cachedImageExistsForURL:(nullable NSURL *)url completion:(nullable SDWebImageCheckCacheCompletionBlock)completionBlock { NSString *key = [self cacheKeyForURL:url]; //内存里面是否有key的缓存 BOOL isInMemoryCache = ([self.imageCache imageFromMemoryCacheForKey:key] != nil); //内存缓存 if (isInMemoryCache) { // making sure we call the completion block on the main queue dispatch_async(dispatch_get_main_queue(), ^{ if (completionBlock) { completionBlock(YES); } }); return; } //磁盘缓存 [self.imageCache diskImageExistsWithKey:key completion:^(BOOL isInDiskCache) { // the completion block of checkDiskCacheForImageWithKey:completion: is always called on the main queue, no need to further dispatch if (completionBlock) { completionBlock(isInDiskCache); } }]; } /** url是否有磁盘缓存数据 @param url url @param completionBlock 缓存结果回调 */ - (void)diskImageExistsForURL:(nullable NSURL *)url completion:(nullable SDWebImageCheckCacheCompletionBlock)completionBlock { NSString *key = [self cacheKeyForURL:url]; [self.imageCache diskImageExistsWithKey:key completion:^(BOOL isInDiskCache) { // the completion block of checkDiskCacheForImageWithKey:completion: is always called on the main queue, no need to further dispatch if (completionBlock) { completionBlock(isInDiskCache); } }]; }
6.3下载(SDWebImage的核心方法)
/** 核心方法。UIView、UIImageView等分类都默认通过调用这个方法来获取数据 @param url 图片的url地址 @param options 获取图片加载处理的属性 @param progressBlock 加载进度回调 @param completedBlock 加载完成回调 @return 返回一个加载的载体对象，以便提供给后面取消删除等 */ - (id <SDWebImageOperation>)loadImageWithURL:(nullable NSURL *)url options:(SDWebImageOptions)options progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDInternalCompletionBlock)completedBlock { // Invoking this method without a completedBlock is pointless //如果想预先下载图片，使用[SDWebImagePrefetcher prefetchURLs]取代本方法。预下载图片是有很多种使用场景的，当我们使用SDWebImagePrefetcher下载图片后，之后使用该图片时就不用从网络上下载了。 NSAssert(completedBlock != nil, @"If you mean to prefetch the image, use -[SDWebImagePrefetcher prefetchURLs] instead"); // Very common mistake is to send the URL using NSString object instead of NSURL. For some strange reason, Xcode won't // throw any warning for this type mismatch. Here we failsafe this error by allowing URLs to be passed as NSString. //如果传入的url是NSString格式的，则转换为NSURL类型再处理 if ([url isKindOfClass:NSString.class]) { url = [NSURL URLWithString:(NSString *)url]; } // Prevents app crashing on argument type error like sending NSNull instead of NSURL //如果url不是NSURL类型的对象，则置为nil if (![url isKindOfClass:NSURL.class]) { url = nil; } //图片加载获取获取过程中绑定一个`SDWebImageCombinedOperation`对象，以方便后续再通过这个对象对url的加载控制。 __block SDWebImageCombinedOperation *operation = [SDWebImageCombinedOperation new]; __weak SDWebImageCombinedOperation *weakOperation = operation; BOOL isFailedUrl = NO; //当前url是否在失败url的集合里面。在图片的下载中，会有一些下载失败的情况，这时候会把这些下载失败的url放到一个集合中去，也就是加入了黑名单，默认是不会再继续下载黑名单中的url了，但是也有例外，当options被设置为SDWebImageRetryFailed的时候，会尝试进行重新下载。 if (url) { @synchronized (self.failedURLs) { isFailedUrl = [self.failedURLs containsObject:url]; } } //如果url长度为0 或者是 失败的url且图片加载处理属性不包含SDWebImageRetryFailed，则直接返回 if (url.absoluteString.length == 0 || (!(options & SDWebImageRetryFailed) && isFailedUrl)) { //构建回调Block [self callCompletionBlockForOperation:operation completion:completedBlock error:[NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorFileDoesNotExist userInfo:nil] url:url]; return operation; } //把加载图片的operation存入runningOperations，里面是所有正在做图片加载过程的operation的集合 @synchronized (self.runningOperations) { [self.runningOperations addObject:operation]; } //根据url获取url对应的key NSString *key = [self cacheKeyForURL:url]; //key为空或者图片从内存中加载，则返回的cacheOperation是nil；其他情况cacheOperation为NSOperation对象 operation.cacheOperation = [self.imageCache queryCacheOperationForKey:key done:^(UIImage *cachedImage, NSData *cachedData, SDImageCacheType cacheType) { //如果已经取消了操作，则直接返回并且移除对应的opetation对象 if (operation.isCancelled) { [self safelyRemoveOperationFromRunning:operation]; return; } //(如果未能在缓存中找到图片||强制刷新缓存) && (代理中未实现图片是否下载的方法||代理中图片是否应该下载方法返回值为YES if ((!cachedImage || options & SDWebImageRefreshCached) && (![self.delegate respondsToSelector:@selector(imageManager:shouldDownloadImageForURL:)] || [self.delegate imageManager:self shouldDownloadImageForURL:url])) { //如果从缓存中获取了图片并且设置了SDWebImageRefreshCached来忽略缓存，则先把缓存的图片返回 if (cachedImage && options & SDWebImageRefreshCached) { // If image was found in the cache but SDWebImageRefreshCached is provided, notify about the cached image // AND try to re-download it in order to let a chance to NSURLCache to refresh it from server. [self callCompletionBlockForOperation:weakOperation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url]; } // download if no image or requested to refresh anyway, and download allowed by delegate //把图片加载的`SDWebImageOptions`类型枚举转换为图片下载的`SDWebImageDownloaderOptions`类型的枚举 SDWebImageDownloaderOptions downloaderOptions = 0; if (options & SDWebImageLowPriority) downloaderOptions |= SDWebImageDownloaderLowPriority; if (options & SDWebImageProgressiveDownload) downloaderOptions |= SDWebImageDownloaderProgressiveDownload; if (options & SDWebImageRefreshCached) downloaderOptions |= SDWebImageDownloaderUseNSURLCache; if (options & SDWebImageContinueInBackground) downloaderOptions |= SDWebImageDownloaderContinueInBackground; if (options & SDWebImageHandleCookies) downloaderOptions |= SDWebImageDownloaderHandleCookies; if (options & SDWebImageAllowInvalidSSLCertificates) downloaderOptions |= SDWebImageDownloaderAllowInvalidSSLCertificates; if (options & SDWebImageHighPriority) downloaderOptions |= SDWebImageDownloaderHighPriority; if (options & SDWebImageScaleDownLargeImages) downloaderOptions |= SDWebImageDownloaderScaleDownLargeImages; //如果设置了强制刷新缓存的选项。则`SDWebImageDownloaderProgressiveDownload`选项失效并且添加`SDWebImageDownloaderIgnoreCachedResponse`选项 if (cachedImage && options & SDWebImageRefreshCached) { // force progressive off if image already cached but forced refreshing downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload; // ignore image read from NSURLCache if image if cached but force refreshing downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse; } //新建一个网络下载的操作 SDWebImageDownloadToken *subOperationToken = [self.imageDownloader downloadImageWithURL:url options:downloaderOptions progress:progressBlock completed:^(UIImage *downloadedImage, NSData *downloadedData, NSError *error, BOOL finished) { __strong __typeof(weakOperation) strongOperation = weakOperation; //如果图片下载结束以后，对应的图片加载操作已经取消。则什么处理都不做 if (!strongOperation || strongOperation.isCancelled) { // Do nothing if the operation was cancelled // See #699 for more details // if we would call the completedBlock, there could be a race condition between this block and another completedBlock for the same object, so if this one is called second, we will overwrite the new data } else if (error) { //如果加载出错，则直接返回回调，并且添加到failedURLs中 [self callCompletionBlockForOperation:strongOperation completion:completedBlock error:error url:url]; if ( error.code != NSURLErrorNotConnectedToInternet && error.code != NSURLErrorCancelled && error.code != NSURLErrorTimedOut && error.code != NSURLErrorInternationalRoamingOff && error.code != NSURLErrorDataNotAllowed && error.code != NSURLErrorCannotFindHost && error.code != NSURLErrorCannotConnectToHost && error.code != NSURLErrorNetworkConnectionLost) { @synchronized (self.failedURLs) { [self.failedURLs addObject:url]; } } } else { //网络图片下载成功 //如果有重试失败下载的选项，则把url从failedURLS中移除 if ((options & SDWebImageRetryFailed)) { @synchronized (self.failedURLs) { [self.failedURLs removeObject:url]; } } //是否需要保存到磁盘 BOOL cacheOnDisk = !(options & SDWebImageCacheMemoryOnly); //如果设置了强制刷新缓存 && 缓存图片存在 && 下载图片不存在，那么直接返回，不执行回调Block if (options & SDWebImageRefreshCached && cachedImage && !downloadedImage) { // Image refresh hit the NSURLCache cache, do not call the completion block } //如果成功下载图片 && 图片是动态图片 && 实现了imageManager:transformDownloadedImage:withURL:代理方法，则进行图片的处理 else if (downloadedImage && (!downloadedImage.images || (options & SDWebImageTransformAnimatedImage)) && [self.delegate respondsToSelector:@selector(imageManager:transformDownloadedImage:withURL:)]) { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ //获取transform以后的图片 UIImage *transformedImage = [self.delegate imageManager:self transformDownloadedImage:downloadedImage withURL:url]; //存储transform以后的的图片 if (transformedImage && finished) { BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage]; // pass nil if the image was transformed, so we can recalculate the data from the image [self.imageCache storeImage:transformedImage imageData:(imageWasTransformed ? nil : downloadedData) forKey:key toDisk:cacheOnDisk completion:nil]; } //回调拼接 [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:transformedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url]; }); } else { //如果成功下载图片，直接缓存和回调 if (downloadedImage && finished) { [self.imageCache storeImage:downloadedImage imageData:downloadedData forKey:key toDisk:cacheOnDisk completion:nil]; } //回调拼接 [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:downloadedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url]; } } //从正在加载的图片操作集合中移除当前操作 if (finished) { [self safelyRemoveOperationFromRunning:strongOperation]; } }]; //重置cancelBlock，取消下载operation operation.cancelBlock = ^{ [self.imageDownloader cancel:subOperationToken]; __strong __typeof(weakOperation) strongOperation = weakOperation; [self safelyRemoveOperationFromRunning:strongOperation]; }; } else if (cachedImage) { //如果获取到了缓存图片，则直接通过缓存图片处理 __strong __typeof(weakOperation) strongOperation = weakOperation; [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url]; [self safelyRemoveOperationFromRunning:operation]; } else { //图片没有缓存并且图片也没有下载 // Image not in cache and download disallowed by delegate __strong __typeof(weakOperation) strongOperation = weakOperation; [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:nil data:nil error:nil cacheType:SDImageCacheTypeNone finished:YES url:url]; [self safelyRemoveOperationFromRunning:operation]; } }]; return operation; }
6.4其他方法
/** 保存图片到缓存 @param image 图片 @param url URL */ - (void)saveImageToCache:(nullable UIImage *)image forURL:(nullable NSURL *)url { if (image && url) { NSString *key = [self cacheKeyForURL:url]; [self.imageCache storeImage:image forKey:key toDisk:YES completion:nil]; } } /** 取消所有的下载 */ - (void)cancelAll { @synchronized (self.runningOperations) { NSArray<SDWebImageCombinedOperation *> *copiedOperations = [self.runningOperations copy]; [copiedOperations makeObjectsPerformSelector:@selector(cancel)]; [self.runningOperations removeObjectsInArray:copiedOperations]; } } /** 查看是否正在执行任务 @return YES/NO */ - (BOOL)isRunning { BOOL isRunning = NO; @synchronized (self.runningOperations) { isRunning = (self.runningOperations.count > 0); } return isRunning; } /** 安全移除任务 @param operation 任务 */ - (void)safelyRemoveOperationFromRunning:(nullable SDWebImageCombinedOperation*)operation { @synchronized (self.runningOperations) { if (operation) { [self.runningOperations removeObject:operation]; } } } /** 拼接回调Block并进行回调 @param operation 任务 @param completionBlock 回调Block @param error error @param url URL */ - (void)callCompletionBlockForOperation:(nullable SDWebImageCombinedOperation*)operation completion:(nullable SDInternalCompletionBlock)completionBlock error:(nullable NSError *)error url:(nullable NSURL *)url { [self callCompletionBlockForOperation:operation completion:completionBlock image:nil data:nil error:error cacheType:SDImageCacheTypeNone finished:YES url:url]; } /** 拼接回调Block并进行回调 @param operation 任务 @param completionBlock 回调Block @param image 图片 @param data 图片数据 @param error error @param cacheType 缓存类型 @param finished 是否完成 @param url URL */ - (void)callCompletionBlockForOperation:(nullable SDWebImageCombinedOperation*)operation completion:(nullable SDInternalCompletionBlock)completionBlock image:(nullable UIImage *)image data:(nullable NSData *)data error:(nullable NSError *)error cacheType:(SDImageCacheType)cacheType finished:(BOOL)finished url:(nullable NSURL *)url { dispatch_main_async_safe(^{ if (operation && !operation.isCancelled && completionBlock) { completionBlock(image, data, error, cacheType, finished, url); } }); }