SDImageCache和SDWebImageDownloader是SDWebImage庫的最重要的兩個部件，它們一起為SDWebImageManager提供服務，來完成圖片的加載。SDImageCache提供了對圖片的內存緩存、異步磁盤緩存、圖片緩存查詢等功能，下載過的圖片會被緩存到內存，也可選擇保存到本地磁盤，當再次請求相同圖片時直接從緩存中讀取圖片，從而大大提高了加載速度。在SDImageCache中，內存緩存是通過 NSCache的子類AutoPurgeCache來實現的；磁盤緩存是通過 NSFileManager 來實現文件的存儲(默認路徑為/Library/Caches/default/com.hackemist.SDWebImageCache.default)，是異步實現的。
下面我們還是一步步來分析它的源碼結構。
1.SDImageCacheType枚舉類型
/** 緩存類型 */ typedef NS_ENUM(NSInteger, SDImageCacheType) { /** * The image wasn't available the SDWebImage caches, but was downloaded from the web. */ SDImageCacheTypeNone, //不使用 SDWebImage 緩存，從網絡下載 /** * The image was obtained from the disk cache. */ SDImageCacheTypeDisk, //使用磁盤緩存 /** * The image was obtained from the memory cache. */ SDImageCacheTypeMemory //使用內存緩存 };
2.Block定義
/** 查詢回調Block @param image 圖片 @param data 圖片數據 @param cacheType 緩存類型 */ typedef void(^SDCacheQueryCompletedBlock)(UIImage * _Nullable image, NSData * _Nullable data, SDImageCacheType cacheType); /** 磁盤緩存檢查回調 @param isInCache 是否在緩存中 */ typedef void(^SDWebImageCheckCacheCompletionBlock)(BOOL isInCache); /** 磁盤緩存空間大小計算回調Block @param fileCount 文件數量 @param totalSize 總大小 */ typedef void(^SDWebImageCalculateSizeBlock)(NSUInteger fileCount, NSUInteger totalSize);
3.SDImageCache的屬性
//SDImageCacheConfig.h @property (assign, nonatomic) BOOL shouldDecompressImages; //!<是否在緩存之前解壓圖片，此項操作可以提升性能，但是會消耗較多的內存，默認是YES。注意:如果內存不足，可以置為NO @property (assign, nonatomic) BOOL shouldDisableiCloud; //!<是否禁止iCloud備份，默認是YES @property (assign, nonatomic) BOOL shouldCacheImagesInMemory; //!<是否啟用內存緩存 默認是YES @property (assign, nonatomic) NSInteger maxCacheAge; //!<磁盤緩存保留的最長時間，默認為1周 @property (assign, nonatomic) NSUInteger maxCacheSize; //!<磁盤緩存最大容量，以字節為單位，默認為0，表示不做限制 //SDImageCache.h @property (nonatomic, nonnull, readonly) SDImageCacheConfig *config; //!<SDImageCacheConfig @property (assign, nonatomic) NSUInteger maxMemoryCost; //!<內存最大容量 @property (assign, nonatomic) NSUInteger maxMemoryCountLimit; //!<緩存中可以存放緩存的最大數量，與NSCache相關 //SDImageCache.m @property (strong, nonatomic, nonnull) NSCache *memCache; //!<內存緩存 @property (strong, nonatomic, nonnull) NSString *diskCachePath; //!<磁盤緩存路徑 @property (strong, nonatomic, nullable) NSMutableArray<NSString *> *customPaths; //!<自定義的緩存路徑 @property (SDDispatchQueueSetterSementics, nonatomic, nullable) dispatch_queue_t ioQueue; //!<磁盤緩存操作的串行隊列
4.SDImageCache的方法
從源碼表面來看，SDImageCache提供的方法很多，但其方法主要圍繞着圖片緩存的添加、刪除、查詢等，只不過每個功能可能有多種實現方式，但本質上是一樣的。
4.1初始化
/** 單例方法，返回一個全局的緩存實例 @return 緩存實例 */ + (nonnull instancetype)sharedImageCache { static dispatch_once_t once; static id instance; dispatch_once(&once, ^{ instance = [self new]; }); return instance; } - (instancetype)init { return [self initWithNamespace:@"default"]; } /** 使用指定的命名空間實例化一個新的緩存存儲 @param ns 命名空間 @return 緩存實例 */ - (nonnull instancetype)initWithNamespace:(nonnull NSString *)ns { NSString *path = [self makeDiskCachePath:ns]; return [self initWithNamespace:ns diskCacheDirectory:path]; } /** 使用指定的命名空間實例化一個新的緩存存儲和目錄 @param ns 命名空間 @param directory 緩存所在目錄 @return 緩存實例 */ - (nonnull instancetype)initWithNamespace:(nonnull NSString *)ns diskCacheDirectory:(nonnull NSString *)directory { if ((self = [super init])) { NSString *fullNamespace = [@"com.hackemist.SDWebImageCache." stringByAppendingString:ns]; // Create IO serial queue _ioQueue = dispatch_queue_create("com.hackemist.SDWebImageCache", DISPATCH_QUEUE_SERIAL); //初始化緩存策略配置對象 _config = [[SDImageCacheConfig alloc] init]; // Init the memory cache // 初始化內存緩存對象 _memCache = [[AutoPurgeCache alloc] init]; _memCache.name = fullNamespace; // 初始化磁盤緩存路徑 if (directory != nil) { _diskCachePath = [directory stringByAppendingPathComponent:fullNamespace]; } else { NSString *path = [self makeDiskCachePath:ns]; _diskCachePath = path; } dispatch_sync(_ioQueue, ^{ _fileManager = [NSFileManager new]; }); #if SD_UIKIT // Subscribe to app events //當應用收到內存警告的時候，清除內存緩存 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(clearMemory) name:UIApplicationDidReceiveMemoryWarningNotification object:nil]; //當應用終止的時候，清除老數據 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(deleteOldFiles) name:UIApplicationWillTerminateNotification object:nil]; //當應用進入后台的時候，在后台刪除老數據 [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(backgroundDeleteOldFiles) name:UIApplicationDidEnterBackgroundNotification object:nil]; #endif } return self; }
上面就是SDImageCache的初始化過程，主要是初始化內存緩存對象和初始化磁盤緩存目錄，以及對一些默認參數的賦值。
4.2緩存圖片
/** 以key為鍵值將圖片image存儲到緩存中 @param image 圖片 @param key key @param completionBlock 回調Block */ - (void)storeImage:(nullable UIImage *)image forKey:(nullable NSString *)key completion:(nullable SDWebImageNoParamsBlock)completionBlock { [self storeImage:image imageData:nil forKey:key toDisk:YES completion:completionBlock]; } /** 以key為鍵值將圖片image存儲到緩存中 @param image 圖片 @param key key @param toDisk 是否寫入磁盤緩存 @param completionBlock 回調Block */ - (void)storeImage:(nullable UIImage *)image forKey:(nullable NSString *)key toDisk:(BOOL)toDisk completion:(nullable SDWebImageNoParamsBlock)completionBlock { [self storeImage:image imageData:nil forKey:key toDisk:toDisk completion:completionBlock]; } /** 把一張圖片存入緩存的具體實現 @param image 緩存的圖片對象 @param imageData 緩存的圖片數據 @param key 緩存對應的key @param toDisk 是否緩存到磁盤 @param completionBlock 緩存完成回調 */ - (void)storeImage:(nullable UIImage *)image imageData:(nullable NSData *)imageData forKey:(nullable NSString *)key toDisk:(BOOL)toDisk completion:(nullable SDWebImageNoParamsBlock)completionBlock { if (!image || !key) { if (completionBlock) { completionBlock(); } return; } // if memory cache is enabled //緩存到內存 if (self.config.shouldCacheImagesInMemory) { //計算緩存數據的大小 NSUInteger cost = SDCacheCostForImage(image); //加入緩存 [self.memCache setObject:image forKey:key cost:cost]; } if (toDisk) { //在一個串行隊列中做磁盤緩存操作 dispatch_async(self.ioQueue, ^{ @autoreleasepool { NSData *data = imageData; if (!data && image) { //獲取圖片的類型GIF/PNG等 SDImageFormat imageFormatFromData = [NSData sd_imageFormatForImageData:data]; //根據指定的SDImageFormat，把圖片轉換為對應的data數據 data = [image sd_imageDataAsFormat:imageFormatFromData]; } //把處理好了的數據存入磁盤 [self storeImageDataToDisk:data forKey:key]; } if (completionBlock) { dispatch_async(dispatch_get_main_queue(), ^{ completionBlock(); }); } }); } else { if (completionBlock) { completionBlock(); } } } /** 把圖片資源存入磁盤 @param imageData 圖片數據 @param key key */ - (void)storeImageDataToDisk:(nullable NSData *)imageData forKey:(nullable NSString *)key { if (!imageData || !key) { return; } [self checkIfQueueIsIOQueue]; //緩存目錄是否已經初始化 if (![_fileManager fileExistsAtPath:_diskCachePath]) { [_fileManager createDirectoryAtPath:_diskCachePath withIntermediateDirectories:YES attributes:nil error:NULL]; } // get cache Path for image key //獲取key對應的完整緩存路徑 NSString *cachePathForKey = [self defaultCachePathForKey:key]; // transform to NSUrl NSURL *fileURL = [NSURL fileURLWithPath:cachePathForKey]; //把數據存入路徑 [_fileManager createFileAtPath:cachePathForKey contents:imageData attributes:nil]; // disable iCloud backup if (self.config.shouldDisableiCloud) { [fileURL setResourceValue:@YES forKey:NSURLIsExcludedFromBackupKey error:nil]; } }
4.3查詢圖片
/** 根據key判斷磁盤緩存中是否存在圖片 @param key key @param completionBlock 回調Block */ - (void)diskImageExistsWithKey:(nullable NSString *)key completion:(nullable SDWebImageCheckCacheCompletionBlock)completionBlock { dispatch_async(_ioQueue, ^{ BOOL exists = [_fileManager fileExistsAtPath:[self defaultCachePathForKey:key]]; // fallback because of https://github.com/rs/SDWebImage/pull/976 that added the extension to the disk file name // checking the key with and without the extension if (!exists) { exists = [_fileManager fileExistsAtPath:[self defaultCachePathForKey:key].stringByDeletingPathExtension]; } if (completionBlock) { dispatch_async(dispatch_get_main_queue(), ^{ completionBlock(exists); }); } }); } /** 根據key獲取緩存在內存中的圖片 @param key key @return 緩存的圖片 */ - (nullable UIImage *)imageFromMemoryCacheForKey:(nullable NSString *)key { return [self.memCache objectForKey:key]; } /** 根據key獲取緩存在磁盤中的圖片 @param key key @return 緩存的圖片 */ - (nullable UIImage *)imageFromDiskCacheForKey:(nullable NSString *)key { UIImage *diskImage = [self diskImageForKey:key]; if (diskImage && self.config.shouldCacheImagesInMemory) { NSUInteger cost = SDCacheCostForImage(diskImage); [self.memCache setObject:diskImage forKey:key cost:cost]; } return diskImage; } /** 根據key獲取緩存圖片(先從內存中搜索，再去磁盤中搜索) @param key key @return 緩存的圖片 */ - (nullable UIImage *)imageFromCacheForKey:(nullable NSString *)key { // First check the in-memory cache... UIImage *image = [self imageFromMemoryCacheForKey:key]; if (image) { return image; } // Second check the disk cache... image = [self imageFromDiskCacheForKey:key]; return image; } /** 根據指定的key，獲取存儲在磁盤上的數據 @param key 圖片對應的key @return 返回圖片數據 */ - (nullable NSData *)diskImageDataBySearchingAllPathsForKey:(nullable NSString *)key { //獲取key對應的path NSString *defaultPath = [self defaultCachePathForKey:key]; NSData *data = [NSData dataWithContentsOfFile:defaultPath]; if (data) { return data; } // fallback because of https://github.com/rs/SDWebImage/pull/976 that added the extension to the disk file name // checking the key with and without the extension //如果key沒有后綴名，則會走到這里通過這里讀取 data = [NSData dataWithContentsOfFile:defaultPath.stringByDeletingPathExtension]; if (data) { return data; } //如果在默認路徑沒有找到圖片，則在自定義路徑迭代查找 NSArray<NSString *> *customPaths = [self.customPaths copy]; for (NSString *path in customPaths) { NSString *filePath = [self cachePathForKey:key inPath:path]; NSData *imageData = [NSData dataWithContentsOfFile:filePath]; if (imageData) { return imageData; } // fallback because of https://github.com/rs/SDWebImage/pull/976 that added the extension to the disk file name // checking the key with and without the extension imageData = [NSData dataWithContentsOfFile:filePath.stringByDeletingPathExtension]; if (imageData) { return imageData; } } return nil; } /** 根據指定的key獲取image對象 @param key key @return image對象 */ - (nullable UIImage *)diskImageForKey:(nullable NSString *)key { //獲取磁盤數據 NSData *data = [self diskImageDataBySearchingAllPathsForKey:key]; if (data) { UIImage *image = [UIImage sd_imageWithData:data]; image = [self scaledImageForKey:key image:image]; if (self.config.shouldDecompressImages) { image = [UIImage decodedImageWithImage:image]; } return image; } else { return nil; } } - (nullable UIImage *)scaledImageForKey:(nullable NSString *)key image:(nullable UIImage *)image { return SDScaledImageForKey(key, image); } /** 在緩存中查詢對應key的數據 @param key 要查詢的key @param doneBlock 查詢結束以后的回調Block @return 返回做查詢操作的NSOperation */ - (nullable NSOperation *)queryCacheOperationForKey:(nullable NSString *)key done:(nullable SDCacheQueryCompletedBlock)doneBlock { if (!key) { if (doneBlock) { doneBlock(nil, nil, SDImageCacheTypeNone); } return nil; } // First check the in-memory cache... //首先從內存中查找圖片 UIImage *image = [self imageFromMemoryCacheForKey:key]; if (image) { NSData *diskData = nil; if ([image isGIF]) { diskData = [self diskImageDataBySearchingAllPathsForKey:key]; } if (doneBlock) { doneBlock(image, diskData, SDImageCacheTypeMemory); } return nil; } //新建一個NSOperation來獲取磁盤圖片 NSOperation *operation = [NSOperation new]; dispatch_async(self.ioQueue, ^{ if (operation.isCancelled) { // do not call the completion if cancelled return; } //在一個自動釋放池中處理圖片從磁盤加載 @autoreleasepool { NSData *diskData = [self diskImageDataBySearchingAllPathsForKey:key]; UIImage *diskImage = [self diskImageForKey:key]; if (diskImage && self.config.shouldCacheImagesInMemory) { NSUInteger cost = SDCacheCostForImage(diskImage); //把從磁盤取出的緩存圖片加入內存緩存中 [self.memCache setObject:diskImage forKey:key cost:cost]; } //圖片處理完成以后回調Block if (doneBlock) { dispatch_async(dispatch_get_main_queue(), ^{ doneBlock(diskImage, diskData, SDImageCacheTypeDisk); }); } } }); return operation; }
4.4刪除圖片
#pragma mark - Remove Ops /** 通過key從磁盤和內存中移除緩存 @param key key @param completion 回調Block */ - (void)removeImageForKey:(nullable NSString *)key withCompletion:(nullable SDWebImageNoParamsBlock)completion { [self removeImageForKey:key fromDisk:YES withCompletion:completion]; } /** 移除指定key對應的緩存數據 @param key key @param fromDisk 是否也清除磁盤緩存 @param completion 回調 */ - (void)removeImageForKey:(nullable NSString *)key fromDisk:(BOOL)fromDisk withCompletion:(nullable SDWebImageNoParamsBlock)completion { if (key == nil) { return; } //移除內存緩存 if (self.config.shouldCacheImagesInMemory) { [self.memCache removeObjectForKey:key]; } //移除磁盤緩存 if (fromDisk) { dispatch_async(self.ioQueue, ^{ [_fileManager removeItemAtPath:[self defaultCachePathForKey:key] error:nil]; if (completion) { dispatch_async(dispatch_get_main_queue(), ^{ completion(); }); } }); } else if (completion){ completion(); } } #pragma mark - Cache clean Ops 內存緩存清理相關操作 /** 清理當前SDImageCache對象的內存緩存 */ - (void)clearMemory { [self.memCache removeAllObjects]; } /** 移除所有的磁盤緩存圖片數據 @param completion 移除完成以后回調 */ - (void)clearDiskOnCompletion:(nullable SDWebImageNoParamsBlock)completion { dispatch_async(self.ioQueue, ^{ [_fileManager removeItemAtPath:self.diskCachePath error:nil]; [_fileManager createDirectoryAtPath:self.diskCachePath withIntermediateDirectories:YES attributes:nil error:NULL]; if (completion) { dispatch_async(dispatch_get_main_queue(), ^{ completion(); }); } }); } - (void)deleteOldFiles { [self deleteOldFilesWithCompletionBlock:nil]; } /** 當應用終止或者進入后台都會調用這個方法來清除緩存圖片 這里會根據圖片存儲時間來清理圖片，默認是一周，從最老的圖片開始清理。如果圖片緩存空間小於一個規定值，則不考慮 @param completionBlock 清除完成以后的回調 */ - (void)deleteOldFilesWithCompletionBlock:(nullable SDWebImageNoParamsBlock)completionBlock { dispatch_async(self.ioQueue, ^{ //獲取磁盤緩存的默認根目錄 NSURL *diskCacheURL = [NSURL fileURLWithPath:self.diskCachePath isDirectory:YES]; NSArray<NSString *> *resourceKeys = @[NSURLIsDirectoryKey, NSURLContentModificationDateKey, NSURLTotalFileAllocatedSizeKey]; // This enumerator prefetches useful properties for our cache files. NSDirectoryEnumerator *fileEnumerator = [_fileManager enumeratorAtURL:diskCacheURL includingPropertiesForKeys:resourceKeys options:NSDirectoryEnumerationSkipsHiddenFiles errorHandler:NULL]; NSDate *expirationDate = [NSDate dateWithTimeIntervalSinceNow:-self.config.maxCacheAge]; NSMutableDictionary<NSURL *, NSDictionary<NSString *, id> *> *cacheFiles = [NSMutableDictionary dictionary]; NSUInteger currentCacheSize = 0; // Enumerate all of the files in the cache directory. This loop has two purposes: // // 1. Removing files that are older than the expiration date. // 2. Storing file attributes for the size-based cleanup pass. //迭代緩存目錄。有兩個目的： //1 刪除比指定日期更老的圖片 //2 記錄文件的大小，以提供給后面刪除使用 NSMutableArray<NSURL *> *urlsToDelete = [[NSMutableArray alloc] init]; for (NSURL *fileURL in fileEnumerator) { NSError *error; //獲取指定url對應文件的指定三種屬性的key和value NSDictionary<NSString *, id> *resourceValues = [fileURL resourceValuesForKeys:resourceKeys error:&error]; // Skip directories and errors. //如果是文件夾則返回 if (error || !resourceValues || [resourceValues[NSURLIsDirectoryKey] boolValue]) { continue; } // Remove files that are older than the expiration date; //獲取指定url文件對應的修改日期 NSDate *modificationDate = resourceValues[NSURLContentModificationDateKey]; //如果修改日期大於指定日期，則加入要移除的數組里 if ([[modificationDate laterDate:expirationDate] isEqualToDate:expirationDate]) { [urlsToDelete addObject:fileURL]; continue; } // Store a reference to this file and account for its total size. //獲取指定的url對應的文件的大小，並且把url與對應大小存入一個字典中 NSNumber *totalAllocatedSize = resourceValues[NSURLTotalFileAllocatedSizeKey]; currentCacheSize += totalAllocatedSize.unsignedIntegerValue; cacheFiles[fileURL] = resourceValues; } //刪除所有最后修改日期大於指定日期的所有文件 for (NSURL *fileURL in urlsToDelete) { [_fileManager removeItemAtURL:fileURL error:nil]; } // If our remaining disk cache exceeds a configured maximum size, perform a second // size-based cleanup pass. We delete the oldest files first. //如果當前緩存的大小超過了默認大小，則按照日期刪除，直到緩存大小<默認大小的一半 if (self.config.maxCacheSize > 0 && currentCacheSize > self.config.maxCacheSize) { // Target half of our maximum cache size for this cleanup pass. const NSUInteger desiredCacheSize = self.config.maxCacheSize / 2; // Sort the remaining cache files by their last modification time (oldest first). //根據文件創建的時間排序 NSArray<NSURL *> *sortedFiles = [cacheFiles keysSortedByValueWithOptions:NSSortConcurrent usingComparator:^NSComparisonResult(id obj1, id obj2) { return [obj1[NSURLContentModificationDateKey] compare:obj2[NSURLContentModificationDateKey]]; }]; // Delete files until we fall below our desired cache size. //迭代刪除緩存，直到緩存大小是默認緩存大小的一半 for (NSURL *fileURL in sortedFiles) { if ([_fileManager removeItemAtURL:fileURL error:nil]) { NSDictionary<NSString *, id> *resourceValues = cacheFiles[fileURL]; NSNumber *totalAllocatedSize = resourceValues[NSURLTotalFileAllocatedSizeKey]; currentCacheSize -= totalAllocatedSize.unsignedIntegerValue; if (currentCacheSize < desiredCacheSize) { break; } } } } //執行完畢，主線程回調 if (completionBlock) { dispatch_async(dispatch_get_main_queue(), ^{ completionBlock(); }); } }); } #if SD_UIKIT /** 應用進入后台的時候，調用這個方法 */ - (void)backgroundDeleteOldFiles { Class UIApplicationClass = NSClassFromString(@"UIApplication"); if(!UIApplicationClass || ![UIApplicationClass respondsToSelector:@selector(sharedApplication)]) { return; } UIApplication *application = [UIApplication performSelector:@selector(sharedApplication)]; //如果backgroundTask對應的時間結束了，任務還沒有處理完成，則直接終止任務 __block UIBackgroundTaskIdentifier bgTask = [application beginBackgroundTaskWithExpirationHandler:^{ // Clean up any unfinished task business by marking where you // stopped or ending the task outright. //當任務非正常終止的時候，做清理工作 [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }]; // Start the long-running task and return immediately. //圖片清理結束以后，處理完成 [self deleteOldFilesWithCompletionBlock:^{ //清理完成以后，終止任務 [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }]; } #endif
4.5其他方法
#pragma mark - Cache paths /** 添加只讀的緩存路徑 @param path 路徑 */ - (void)addReadOnlyCachePath:(nonnull NSString *)path { if (!self.customPaths) { self.customPaths = [NSMutableArray new]; } if (![self.customPaths containsObject:path]) { [self.customPaths addObject:path]; } } /** 獲取指定key對應的完整緩存路徑 @param key 對應一張圖片，比如圖片的名字 @param path 指定根目錄 @return 完整路徑 */ - (nullable NSString *)cachePathForKey:(nullable NSString *)key inPath:(nonnull NSString *)path { NSString *filename = [self cachedFileNameForKey:key]; return [path stringByAppendingPathComponent:filename]; } - (nullable NSString *)defaultCachePathForKey:(nullable NSString *)key { return [self cachePathForKey:key inPath:self.diskCachePath]; } /** MD5加密 @param key key @return 加密后的數據 */ - (nullable NSString *)cachedFileNameForKey:(nullable NSString *)key { const char *str = key.UTF8String; if (str == NULL) { str = ""; } unsigned char r[CC_MD5_DIGEST_LENGTH]; CC_MD5(str, (CC_LONG)strlen(str), r); NSString *filename = [NSString stringWithFormat:@"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%@", r[0], r[1], r[2], r[3], r[4], r[5], r[6], r[7], r[8], r[9], r[10], r[11], r[12], r[13], r[14], r[15], [key.pathExtension isEqualToString:@""] ? @"" : [NSString stringWithFormat:@".%@", key.pathExtension]]; return filename; } /** 圖片緩存目錄 @param fullNamespace 自定義子目錄名稱 @return 完整目錄 */ - (nullable NSString *)makeDiskCachePath:(nonnull NSString*)fullNamespace { NSArray<NSString *> *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES); return [paths[0] stringByAppendingPathComponent:fullNamespace]; } #pragma mark - Cache Info /** 磁盤緩存使用的大小 @return 磁盤緩存的大小 */ - (NSUInteger)getSize { __block NSUInteger size = 0; dispatch_sync(self.ioQueue, ^{ NSDirectoryEnumerator *fileEnumerator = [_fileManager enumeratorAtPath:self.diskCachePath]; for (NSString *fileName in fileEnumerator) { NSString *filePath = [self.diskCachePath stringByAppendingPathComponent:fileName]; NSDictionary<NSString *, id> *attrs = [[NSFileManager defaultManager] attributesOfItemAtPath:filePath error:nil]; size += [attrs fileSize]; } }); return size; } /** 磁盤緩存的圖片數量 @return 緩存的圖片數量 */ - (NSUInteger)getDiskCount { __block NSUInteger count = 0; dispatch_sync(self.ioQueue, ^{ NSDirectoryEnumerator *fileEnumerator = [_fileManager enumeratorAtPath:self.diskCachePath]; count = fileEnumerator.allObjects.count; }); return count; } /** 異步計算磁盤緩存的大小 @param completionBlock 回調Block */ - (void)calculateSizeWithCompletionBlock:(nullable SDWebImageCalculateSizeBlock)completionBlock { NSURL *diskCacheURL = [NSURL fileURLWithPath:self.diskCachePath isDirectory:YES]; dispatch_async(self.ioQueue, ^{ NSUInteger fileCount = 0; NSUInteger totalSize = 0; NSDirectoryEnumerator *fileEnumerator = [_fileManager enumeratorAtURL:diskCacheURL includingPropertiesForKeys:@[NSFileSize] options:NSDirectoryEnumerationSkipsHiddenFiles errorHandler:NULL]; for (NSURL *fileURL in fileEnumerator) { NSNumber *fileSize; [fileURL getResourceValue:&fileSize forKey:NSURLFileSizeKey error:NULL]; totalSize += fileSize.unsignedIntegerValue; fileCount += 1; } if (completionBlock) { dispatch_async(dispatch_get_main_queue(), ^{ completionBlock(fileCount, totalSize); }); } }); }