SDWebImage 源碼解讀（二）：Manager
書接上文，在經過 WebCache Categories 調用了 sd_setImageWithURL:placeholderImage: 等方法後，都會彙總到 SDWebImageManager 的 loadImageWithURL:options:context:progress:completed: 方法中。SDWebImageManager 類是整個 SDWebImage 的核心管理類，負責協調下載和緩存的關係，接下來咱們就一步步的分析其源代碼，探究其實現。git
初始化方法
SDWebImageManager 的指定初始化方法聲明和實現以下：github
/** * Allows to specify instance of cache and image loader used with image manager. * @return new instance of `SDWebImageManager` with specified cache and loader. */
- (nonnull instancetype)initWithCache:(nonnull id<SDImageCache>)cache loader:(nonnull id<SDImageLoader>)loader NS_DESIGNATED_INITIALIZER;
- (nonnull instancetype)initWithCache:(nonnull id<SDImageCache>)cache loader:(nonnull id<SDImageLoader>)loader {
if ((self = [super init])) {
_imageCache = cache;
_imageLoader = loader;
_failedURLs = [NSMutableSet new];
_failedURLsLock = dispatch_semaphore_create(1);
_runningOperations = [NSMutableSet new];
_runningOperationsLock = dispatch_semaphore_create(1);
}
return self;
}
複製代碼
不過在最簡單的使用方法中，SDWebImage 是看成單例來使用的，相關代碼以下：緩存
/** * Returns global shared manager instance. */
@property (nonatomic, class, readonly, nonnull) SDWebImageManager *sharedManager;
+ (nonnull instancetype)sharedManager {
static dispatch_once_t once;
static id instance;
dispatch_once(&once, ^{
instance = [self new];
});
return instance;
}
- (nonnull instancetype)init {
id<SDImageCache> cache = [[self class] defaultImageCache];
if (!cache) {
cache = [SDImageCache sharedImageCache];
}
id<SDImageLoader> loader = [[self class] defaultImageLoader];
if (!loader) {
loader = [SDWebImageDownloader sharedDownloader];
}
return [self initWithCache:cache loader:loader];
}
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在 init 方法中，cache 和 loader 會先經過類方法進行查找，若是找不到再使用 SDImageChche 和 SDWebImageDownloader 的單例，相關代碼以下所示：安全
/** The default image cache when the manager which is created with no arguments. Such as shared manager or init. Defaults to nil. Means using `SDImageCache.sharedImageCache` */
@property (nonatomic, class, nullable) id<SDImageCache> defaultImageCache;
/** The default image loader for manager which is created with no arguments. Such as shared manager or init. Defaults to nil. Means using `SDWebImageDownloader.sharedDownloader` */
@property (nonatomic, class, nullable) id<SDImageLoader> defaultImageLoader;
static id<SDImageCache> _defaultImageCache;
static id<SDImageLoader> _defaultImageLoader;
+ (id<SDImageCache>)defaultImageCache {
return _defaultImageCache;
}
+ (void)setDefaultImageCache:(id<SDImageCache>)defaultImageCache {
if (defaultImageCache && ![defaultImageCache conformsToProtocol:@protocol(SDImageCache)]) {
return;
}
_defaultImageCache = defaultImageCache;
}
+ (id<SDImageLoader>)defaultImageLoader {
return _defaultImageLoader;
}
+ (void)setDefaultImageLoader:(id<SDImageLoader>)defaultImageLoader {
if (defaultImageLoader && ![defaultImageLoader conformsToProtocol:@protocol(SDImageLoader)]) {
return;
}
_defaultImageLoader = defaultImageLoader;
}
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加載圖片
加載圖片分爲兩個步驟，首先回去 cache 裏面查找圖片，若是沒有再進行下載，方法的聲明以下：併發
/** * Downloads the image at the given URL if not present in cache or return the cached version otherwise. * * @param url The URL to the image * @param options A mask to specify options to use for this request * @param context A context contains different options to perform specify changes or processes, see `SDWebImageContextOption`. This hold the extra objects which `options` enum can not hold. * @param progressBlock A block called while image is downloading * @note the progress block is executed on a background queue * @param completedBlock A block called when operation has been completed. * * @return Returns an instance of SDWebImageCombinedOperation, which you can cancel the loading process. */
- (nullable SDWebImageCombinedOperation *)loadImageWithURL:(nullable NSURL *)url
options:(SDWebImageOptions)options
context:(nullable SDWebImageContext *)context
progress:(nullable SDImageLoaderProgressBlock)progressBlock
completed:(nonnull SDInternalCompletionBlock)completedBlock;
複製代碼
方法實現以下：app
- (SDWebImageCombinedOperation *)loadImageWithURL:(nullable NSURL *)url
options:(SDWebImageOptions)options
context:(nullable SDWebImageContext *)context
progress:(nullable SDImageLoaderProgressBlock)progressBlock
completed:(nonnull SDInternalCompletionBlock)completedBlock {
// Invoking this method without a completedBlock is pointless
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.
if ([url isKindOfClass:NSString.class]) {
url = [NSURL URLWithString:(NSString *)url];
}
// Prevents app crashing on argument type error like sending NSNull instead of NSURL
if (![url isKindOfClass:NSURL.class]) {
url = nil;
}
// 建立一個 SDWebImageCombinedOperation 實例
SDWebImageCombinedOperation *operation = [SDWebImageCombinedOperation new];
operation.manager = self;
// 查詢該 url 是不是下載失敗過的 url
BOOL isFailedUrl = NO;
if (url) {
SD_LOCK(self.failedURLsLock);
isFailedUrl = [self.failedURLs containsObject:url];
SD_UNLOCK(self.failedURLsLock);
}
// 若是 url 內容爲空，或者沒有設置失敗重試且當前 url 下載失敗過，走失敗回調
if (url.absoluteString.length == 0 || (!(options & SDWebImageRetryFailed) && isFailedUrl)) {
[self callCompletionBlockForOperation:operation completion:completedBlock error:[NSError errorWithDomain:SDWebImageErrorDomain code:SDWebImageErrorInvalidURL userInfo:@{NSLocalizedDescriptionKey : @"Image url is nil"}] url:url];
return operation;
}
// 把當前 operation 放入 runningOperations 集合中
SD_LOCK(self.runningOperationsLock);
[self.runningOperations addObject:operation];
SD_UNLOCK(self.runningOperationsLock);
// Preprocess the options and context arg to decide the final the result for manager
SDWebImageOptionsResult *result = [self processedResultForURL:url options:options context:context];
// Start the entry to load image from cache
[self callCacheProcessForOperation:operation url:url options:result.options context:result.context progress:progressBlock completed:completedBlock];
return operation;
}
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SDWebImageCombinedOperation
SDWebImageCombinedOperation 是每次進行圖片加載都會使用到的實例，其聲明以下：框架
/** A combined operation representing the cache and loader operation. You can use it to cancel the load process. */
@interface SDWebImageCombinedOperation : NSObject <SDWebImageOperation>
/** Cancel the current operation, including cache and loader process */
- (void)cancel;
/** The cache operation from the image cache query */
@property (strong, nonatomic, nullable, readonly) id<SDWebImageOperation> cacheOperation;
/** The loader operation from the image loader (such as download operation) */
@property (strong, nonatomic, nullable, readonly) id<SDWebImageOperation> loaderOperation;
@end
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其 cancel 方法實現以下：less
- (void)cancel {
@synchronized(self) {
if (self.isCancelled) {
return;
}
self.cancelled = YES;
if (self.cacheOperation) {
[self.cacheOperation cancel];
self.cacheOperation = nil;
}
if (self.loaderOperation) {
[self.loaderOperation cancel];
self.loaderOperation = nil;
}
[self.manager safelyRemoveOperationFromRunning:self];
}
}
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SDWebImageCombinedOperation 遵照了 SDWebImageOperation 協議，且包含了標示查找緩存的 cacheOperation 和下載的 loaderOperation，本質上就是模型類。dom
SD_LOCK & SD_UNLOCK
Objective-C 提供的集合類都不是線程安全的，因此須要加鎖，SDWebImage 是經過 dispatch_semaphore_t 來當作鎖使用的，好比：async
@property (strong, nonatomic, nonnull) dispatch_semaphore_t failedURLsLock; // a lock to keep the access to `failedURLs` thread-safe
@property (strong, nonatomic, nonnull) dispatch_semaphore_t runningOperationsLock; // a lock to keep the access to `runningOperations` thread-safe
複製代碼
SD_LOCK 和 SD_UNLOCK 則是兩個宏，用於配合 dispatch_semaphore_t 達到鎖的調用方式和效果：
#ifndef SD_LOCK
#define SD_LOCK(lock) dispatch_semaphore_wait(lock, DISPATCH_TIME_FOREVER);
#endif
#ifndef SD_UNLOCK
#define SD_UNLOCK(lock) dispatch_semaphore_signal(lock);
#endif
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失敗回調
當出現錯誤時，會調用 callCompletionBlockForOperation:completion:error:url:，以下：
- (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];
}
- (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);
}
});
}
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SDWebImageOptionsResult
SDWebImageOptionsResult 是一個模型類，在這裏是爲了統一 options 和 context 並對其進行統一配置，若是 context 裏有，就用 context 裏的，若是沒有就用 SDWebImageManager 裏的。同時若是 optionsProcessor 存在，則使用 optionsProcessor 生成 SDWebImageOptionsResult 實例。
- (SDWebImageOptionsResult *)processedResultForURL:(NSURL *)url options:(SDWebImageOptions)options context:(SDWebImageContext *)context {
SDWebImageOptionsResult *result;
SDWebImageMutableContext *mutableContext = [SDWebImageMutableContext dictionary];
// Image Transformer from manager
if (!context[SDWebImageContextImageTransformer]) {
id<SDImageTransformer> transformer = self.transformer;
[mutableContext setValue:transformer forKey:SDWebImageContextImageTransformer];
}
// Cache key filter from manager
if (!context[SDWebImageContextCacheKeyFilter]) {
id<SDWebImageCacheKeyFilter> cacheKeyFilter = self.cacheKeyFilter;
[mutableContext setValue:cacheKeyFilter forKey:SDWebImageContextCacheKeyFilter];
}
// Cache serializer from manager
if (!context[SDWebImageContextCacheSerializer]) {
id<SDWebImageCacheSerializer> cacheSerializer = self.cacheSerializer;
[mutableContext setValue:cacheSerializer forKey:SDWebImageContextCacheSerializer];
}
if (mutableContext.count > 0) {
if (context) {
[mutableContext addEntriesFromDictionary:context];
}
context = [mutableContext copy];
}
// Apply options processor
if (self.optionsProcessor) {
result = [self.optionsProcessor processedResultForURL:url options:options context:context];
}
if (!result) {
// Use default options result
result = [[SDWebImageOptionsResult alloc] initWithOptions:options context:context];
}
return result;
}
複製代碼
optionsProcessor 是一個遵照了 SDWebImageOptionsProcessor 協議的處理模塊，用於咱們自定義配置。
開啓加載圖片
在方法的最後調用 callCacheProcessForOperation:url:options:context:progress:completed:，正式進入加載圖片操做：
// Query cache process
- (void)callCacheProcessForOperation:(nonnull SDWebImageCombinedOperation *)operation
url:(nonnull NSURL *)url
options:(SDWebImageOptions)options
context:(nullable SDWebImageContext *)context
progress:(nullable SDImageLoaderProgressBlock)progressBlock
completed:(nullable SDInternalCompletionBlock)completedBlock {
// Check whether we should query cache
BOOL shouldQueryCache = (options & SDWebImageFromLoaderOnly) == 0;
if (shouldQueryCache) {
id<SDWebImageCacheKeyFilter> cacheKeyFilter = context[SDWebImageContextCacheKeyFilter]; // 從 context 中取得 cacheKeyFilter
NSString *key = [self cacheKeyForURL:url cacheKeyFilter:cacheKeyFilter]; // 獲取圖片緩存的 key
@weakify(operation); // 從 imageCache 中查找圖片
operation.cacheOperation = [self.imageCache queryImageForKey:key options:options context:context completion:^(UIImage * _Nullable cachedImage, NSData * _Nullable cachedData, SDImageCacheType cacheType) {
@strongify(operation);
if (!operation || operation.isCancelled) { // 若是 operation 爲空或已經取消，直接從隊列中移除 operation
[self safelyRemoveOperationFromRunning:operation];
return;
}
// Continue download process
[self callDownloadProcessForOperation:operation url:url options:options context:context cachedImage:cachedImage cachedData:cachedData cacheType:cacheType progress:progressBlock completed:completedBlock];
}];
} else {
// Continue download process
[self callDownloadProcessForOperation:operation url:url options:options context:context cachedImage:nil cachedData:nil cacheType:SDImageCacheTypeNone progress:progressBlock completed:completedBlock];
}
}
複製代碼
獲取圖片緩存的 key
- (nullable NSString *)cacheKeyForURL:(nullable NSURL *)url cacheKeyFilter:(id<SDWebImageCacheKeyFilter>)cacheKeyFilter {
if (!url) {
return @"";
}
if (cacheKeyFilter) {
return [cacheKeyFilter cacheKeyForURL:url];
} else {
return url.absoluteString;
}
}
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從操做隊列中移除 operation
- (void)safelyRemoveOperationFromRunning:(nullable SDWebImageCombinedOperation*)operation {
if (!operation) {
return;
}
SD_LOCK(self.runningOperationsLock);
[self.runningOperations removeObject:operation];
SD_UNLOCK(self.runningOperationsLock);
}
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下載圖片
在從緩存中沒能查找出圖片的時候，會進入下載操做階段，方法實現以下：
// Download process
- (void)callDownloadProcessForOperation:(nonnull SDWebImageCombinedOperation *)operation
url:(nonnull NSURL *)url
options:(SDWebImageOptions)options
context:(SDWebImageContext *)context
cachedImage:(nullable UIImage *)cachedImage
cachedData:(nullable NSData *)cachedData
cacheType:(SDImageCacheType)cacheType
progress:(nullable SDImageLoaderProgressBlock)progressBlock
completed:(nullable SDInternalCompletionBlock)completedBlock {
// Check whether we should download image from network
BOOL shouldDownload = (options & SDWebImageFromCacheOnly) == 0; // 查看是否設置了只從緩存中找
shouldDownload &= (!cachedImage || options & SDWebImageRefreshCached); // 查看緩存圖片是否爲 nil，且設置了刷新緩存標誌位
shouldDownload &= (![self.delegate respondsToSelector:@selector(imageManager:shouldDownloadImageForURL:)] || [self.delegate imageManager:self shouldDownloadImageForURL:url]); // 查看代理方法是否被實現並取得結果
shouldDownload &= [self.imageLoader canRequestImageForURL:url]; // 查看 URL 是否能夠被請求
if (shouldDownload) {
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:operation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url];
// Pass the cached image to the image loader. The image loader should check whether the remote image is equal to the cached image.
SDWebImageMutableContext *mutableContext;
if (context) {
mutableContext = [context mutableCopy];
} else {
mutableContext = [NSMutableDictionary dictionary];
}
mutableContext[SDWebImageContextLoaderCachedImage] = cachedImage;
context = [mutableContext copy];
}
// `SDWebImageCombinedOperation` -> `SDWebImageDownloadToken` -> `downloadOperationCancelToken`, which is a `SDCallbacksDictionary` and retain the completed block below, so we need weak-strong again to avoid retain cycle
@weakify(operation);
operation.loaderOperation = [self.imageLoader requestImageWithURL:url options:options context:context progress:progressBlock completed:^(UIImage *downloadedImage, NSData *downloadedData, NSError *error, BOOL finished) {
@strongify(operation);
if (!operation || operation.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 (cachedImage && options & SDWebImageRefreshCached && [error.domain isEqualToString:SDWebImageErrorDomain] && error.code == SDWebImageErrorCacheNotModified) {
// Image refresh hit the NSURLCache cache, do not call the completion block
} else if (error) {
[self callCompletionBlockForOperation:operation completion:completedBlock error:error url:url];
BOOL shouldBlockFailedURL = [self shouldBlockFailedURLWithURL:url error:error];
if (shouldBlockFailedURL) {
SD_LOCK(self.failedURLsLock);
[self.failedURLs addObject:url];
SD_UNLOCK(self.failedURLsLock);
}
} else {
if ((options & SDWebImageRetryFailed)) {
SD_LOCK(self.failedURLsLock);
[self.failedURLs removeObject:url];
SD_UNLOCK(self.failedURLsLock);
}
[self callStoreCacheProcessForOperation:operation url:url options:options context:context downloadedImage:downloadedImage downloadedData:downloadedData finished:finished progress:progressBlock completed:completedBlock];
}
if (finished) {
[self safelyRemoveOperationFromRunning:operation];
}
}];
} else if (cachedImage) {
[self callCompletionBlockForOperation:operation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url];
[self safelyRemoveOperationFromRunning:operation];
} else {
// Image not in cache and download disallowed by delegate
[self callCompletionBlockForOperation:operation completion:completedBlock image:nil data:nil error:nil cacheType:SDImageCacheTypeNone finished:YES url:url];
[self safelyRemoveOperationFromRunning:operation];
}
}
複製代碼
主要內容就是啓動下載，並根據結果走不一樣的路徑來處理圖片。若是走最主要的路徑，則還要在下載完成後去進行圖片存儲。
圖片存儲
// Store cache process
- (void)callStoreCacheProcessForOperation:(nonnull SDWebImageCombinedOperation *)operation
url:(nonnull NSURL *)url
options:(SDWebImageOptions)options
context:(SDWebImageContext *)context
downloadedImage:(nullable UIImage *)downloadedImage
downloadedData:(nullable NSData *)downloadedData
finished:(BOOL)finished
progress:(nullable SDImageLoaderProgressBlock)progressBlock
completed:(nullable SDInternalCompletionBlock)completedBlock {
// the target image store cache type
SDImageCacheType storeCacheType = SDImageCacheTypeAll;
if (context[SDWebImageContextStoreCacheType]) {
storeCacheType = [context[SDWebImageContextStoreCacheType] integerValue];
}
// the original store image cache type
SDImageCacheType originalStoreCacheType = SDImageCacheTypeNone;
if (context[SDWebImageContextOriginalStoreCacheType]) {
originalStoreCacheType = [context[SDWebImageContextOriginalStoreCacheType] integerValue];
}
id<SDWebImageCacheKeyFilter> cacheKeyFilter = context[SDWebImageContextCacheKeyFilter];
NSString *key = [self cacheKeyForURL:url cacheKeyFilter:cacheKeyFilter];
id<SDImageTransformer> transformer = context[SDWebImageContextImageTransformer];
id<SDWebImageCacheSerializer> cacheSerializer = context[SDWebImageContextCacheSerializer];
BOOL shouldTransformImage = downloadedImage && (!downloadedImage.sd_isAnimated || (options & SDWebImageTransformAnimatedImage)) && transformer;
BOOL shouldCacheOriginal = downloadedImage && finished;
// if available, store original image to cache
if (shouldCacheOriginal) {
// normally use the store cache type, but if target image is transformed, use original store cache type instead
SDImageCacheType targetStoreCacheType = shouldTransformImage ? originalStoreCacheType : storeCacheType;
if (cacheSerializer && (targetStoreCacheType == SDImageCacheTypeDisk || targetStoreCacheType == SDImageCacheTypeAll)) { // 若是 cacheSerializer 不爲空，則在全局併發隊列中處理存儲操做
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
@autoreleasepool {
NSData *cacheData = [cacheSerializer cacheDataWithImage:downloadedImage originalData:downloadedData imageURL:url];
[self.imageCache storeImage:downloadedImage imageData:cacheData forKey:key cacheType:targetStoreCacheType completion:nil];
}
});
} else {
[self.imageCache storeImage:downloadedImage imageData:downloadedData forKey:key cacheType:targetStoreCacheType completion:nil];
}
}
// if available, store transformed image to cache
if (shouldTransformImage) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
@autoreleasepool {
UIImage *transformedImage = [transformer transformedImageWithImage:downloadedImage forKey:key]; // 使用 transformer 處理圖片以後再進行存儲
if (transformedImage && finished) {
NSString *transformerKey = [transformer transformerKey];
NSString *cacheKey = SDTransformedKeyForKey(key, transformerKey);
BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage];
NSData *cacheData;
// pass nil if the image was transformed, so we can recalculate the data from the image
if (cacheSerializer && (storeCacheType == SDImageCacheTypeDisk || storeCacheType == SDImageCacheTypeAll)) {
cacheData = [cacheSerializer cacheDataWithImage:transformedImage originalData:(imageWasTransformed ? nil : downloadedData) imageURL:url];
} else {
cacheData = (imageWasTransformed ? nil : downloadedData);
}
[self.imageCache storeImage:transformedImage imageData:cacheData forKey:cacheKey cacheType:storeCacheType completion:nil];
}
[self callCompletionBlockForOperation:operation completion:completedBlock image:transformedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url];
}
});
} else {
[self callCompletionBlockForOperation:operation completion:completedBlock image:downloadedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url];
}
}
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SDImageTransformer
SDImageTransformer 是一個協議，聲明以下：
/** A transformer protocol to transform the image load from cache or from download. You can provide transformer to cache and manager (Through the `transformer` property or context option `SDWebImageContextImageTransformer`). @note The transform process is called from a global queue in order to not to block the main queue. */
@protocol SDImageTransformer <NSObject>
@required
/** For each transformer, it must contains its cache key to used to store the image cache or query from the cache. This key will be appened after the original cache key generated by URL or from user. @return The cache key to appended after the original cache key. Should not be nil. */
@property (nonatomic, copy, readonly, nonnull) NSString *transformerKey;
/** Transform the image to another image. @param image The image to be transformed @param key The cache key associated to the image @return The transformed image, or nil if transform failed */
- (nullable UIImage *)transformedImageWithImage:(nonnull UIImage *)image forKey:(nonnull NSString *)key;
@end
複製代碼
在圖片下載完成後，咱們可能但願對將要緩存的圖片作一些處理，好比下載的是頭像數據，可能會直接切成圓角存儲起來，這樣避免了之後每次使用圖片都要設置帶來的困擾。SDWebImage 框架爲咱們默認實現了一些，例如 SDImagePipelineTransformer，用於將多個 Transformer 當作渲染管線使用。還有 SDImageRoundCornerTransformer，用於對下載好的圖片進行圓角處理等等。
SDWebImageCacheSerializer
SDWebImageCacheSerializer 也是一個協議，能夠對即將緩存的圖片的數據進行一些處理。
/** This is the protocol for cache serializer. We can use a block to specify the cache serializer. But Using protocol can make this extensible, and allow Swift user to use it easily instead of using `@convention(block)` to store a block into context options. */
@protocol SDWebImageCacheSerializer <NSObject>
- (nullable NSData *)cacheDataWithImage:(nonnull UIImage *)image originalData:(nullable NSData *)data imageURL:(nullable NSURL *)imageURL;
@end
複製代碼
以上就是 Manager 主流程中的全部代碼了。
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