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遵循于： NSObject

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声明处：SDWebImageDownloaderOperation.h

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概述

描述一个下载操作。如果想使用一个自定义的下载操作，需要继承NSOpertaion并遵循这些协议。

任务

• - initWithRequest:inSession:options: 必须实现
• - addHandlerForProgress:completed: 必须实现
• shouldDecompressImages: 必须实现
• setShouldDecompressImages: 必须实现
• credential 必须实现
• setCredential: 必须实现

实例方法

addHandlersForProgress:completed:

- (nullable id)addHandlersForProgress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock

credential

- (nullable NSURLCredential *)credential

initWithRequest:inSession:options:

- (nonnull instancetype)initWithRequest:(nullable NSURLRequest *)request inSession:(nullable NSURLSession *)session options:(SDWebImageDownloaderOptions)options

setCredential:

- (void)setCredential:(nullable NSURLCredential *)value

setShouldDecompressImages:

- (void)setShouldDecompressImages:(BOOL)value

shouldDecompressImages

- (BOOL)shouldDecompressImages

// END 呵呵哒，文档中都不需要解析怎么用，只要实现就好的。