该文章阅读的SDWebImage的版本为4.3.3。

这个分类提供了为UIButton设置网络图像的快捷方法。

1.公共方法

1.1.设置image的方法

/**
 获取当前图像链接地址
 */
- (nullable NSURL *)sd_currentImageURL;

/**
 获取指定状态图像链接地址
 */
- (nullable NSURL *)sd_imageURLForState:(UIControlState)state;

/**
 设置指定状态的图像链接地址
 */
- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的图像链接地址和占位图
 */
- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state
          placeholderImage:(nullable UIImage *)placeholder NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的图像链接地址和占位图以及可选项
 */
- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state
          placeholderImage:(nullable UIImage *)placeholder
                   options:(SDWebImageOptions)options NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的图像链接地址和完成回调
 */
- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state
                 completed:(nullable SDExternalCompletionBlock)completedBlock;

/**
 设置指定状态的图像链接地址和占位图以及完成回调
 */
- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state
          placeholderImage:(nullable UIImage *)placeholder
                 completed:(nullable SDExternalCompletionBlock)completedBlock NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的图像链接地址、占位图、可选项以及完成回调
 */
- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state
          placeholderImage:(nullable UIImage *)placeholder
                   options:(SDWebImageOptions)options
                 completed:(nullable SDExternalCompletionBlock)completedBlock;

1.2.设置background image的方法

/**
 获取当前背景图像链接地址
 */
- (nullable NSURL *)sd_currentBackgroundImageURL;

/**
 获取指定状态背景图像链接地址
 */
- (nullable NSURL *)sd_backgroundImageURLForState:(UIControlState)state;

/**
 设置指定状态的背景图像链接地址
 */
- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的背景图像链接地址和占位图
 */
- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state
                    placeholderImage:(nullable UIImage *)placeholder NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的背景图像链接地址和占位图以及可选项
 */
- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state
                    placeholderImage:(nullable UIImage *)placeholder
                             options:(SDWebImageOptions)options NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的背景图像链接地址和占位图以及完成回调
 */
- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state
                           completed:(nullable SDExternalCompletionBlock)completedBlock;

/**
 设置指定状态的背景图像链接地址和占位图以及完成回调
 */
- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state
                    placeholderImage:(nullable UIImage *)placeholder
                           completed:(nullable SDExternalCompletionBlock)completedBlock NS_REFINED_FOR_SWIFT;

/**
 设置指定状态的背景图像链接地址、占位图、可选项以及完成回调
 */
- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state
                    placeholderImage:(nullable UIImage *)placeholder
                             options:(SDWebImageOptions)options
                           completed:(nullable SDExternalCompletionBlock)completedBlock;

1.3.取消网络图像加载的方法

/**
 取消指定状态当前图像的网络加载
 */
- (void)sd_cancelImageLoadForState:(UIControlState)state;

/**
 取消指定状态当前背景图像的网络加载
 */
- (void)sd_cancelBackgroundImageLoadForState:(UIControlState)state;

2.私有静态函数

/**
 获取指定状态的图像链接键
 */
static inline NSString * imageURLKeyForState(UIControlState state) {
    return [NSString stringWithFormat:@"image_%lu", (unsigned long)state];
}

/**
 获取指定状态的背景图像链接键
 */
static inline NSString * backgroundImageURLKeyForState(UIControlState state) {
    return [NSString stringWithFormat:@"backgroundImage_%lu", (unsigned long)state];
}

/**
 获取指定状态的图像选项键
 */
static inline NSString * imageOperationKeyForState(UIControlState state) {
    return [NSString stringWithFormat:@"UIButtonImageOperation%lu", (unsigned long)state];
}

/**
 获取指定状态的背景图像选项键
 */
static inline NSString * backgroundImageOperationKeyForState(UIControlState state) {
    return [NSString stringWithFormat:@"UIButtonBackgroundImageOperation%lu", (unsigned long)state];
}

3.私有方法

/**
 获取保存图像链接的字典对象
 */
- (SDStateImageURLDictionary *)sd_imageURLStorage {
    SDStateImageURLDictionary *storage = objc_getAssociatedObject(self, &imageURLStorageKey);
    if (!storage) {
        storage = [NSMutableDictionary dictionary];
        objc_setAssociatedObject(self, &imageURLStorageKey, storage, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }

    return storage;
}

4.实现

4.1.设置image的方法实现

- (nullable NSURL *)sd_currentImageURL {
    // 获取当前状态的图像地址
    NSURL *url = self.sd_imageURLStorage[imageURLKeyForState(self.state)];

    // 如果没有就获取普通状态的图像地址
    if (!url) {
        url = self.sd_imageURLStorage[imageURLKeyForState(UIControlStateNormal)];
    }

    return url;
}

- (nullable NSURL *)sd_imageURLForState:(UIControlState)state {
    // 获取指定状态的图像地址
    return self.sd_imageURLStorage[imageURLKeyForState(state)];
}

- (void)sd_setImageWithURL:(nullable NSURL *)url forState:(UIControlState)state {
    // 调用全能方法
    [self sd_setImageWithURL:url forState:state placeholderImage:nil options:0 completed:nil];
}

- (void)sd_setImageWithURL:(nullable NSURL *)url forState:(UIControlState)state placeholderImage:(nullable UIImage *)placeholder {
    // 调用全能方法
    [self sd_setImageWithURL:url forState:state placeholderImage:placeholder options:0 completed:nil];
}

- (void)sd_setImageWithURL:(nullable NSURL *)url forState:(UIControlState)state placeholderImage:(nullable UIImage *)placeholder options:(SDWebImageOptions)options {
    [self sd_setImageWithURL:url forState:state placeholderImage:placeholder options:options completed:nil];
}

- (void)sd_setImageWithURL:(nullable NSURL *)url forState:(UIControlState)state completed:(nullable SDExternalCompletionBlock)completedBlock {
    // 调用全能方法
    [self sd_setImageWithURL:url forState:state placeholderImage:nil options:0 completed:completedBlock];
}

- (void)sd_setImageWithURL:(nullable NSURL *)url forState:(UIControlState)state placeholderImage:(nullable UIImage *)placeholder completed:(nullable SDExternalCompletionBlock)completedBlock {
    // 调用全能方法
    [self sd_setImageWithURL:url forState:state placeholderImage:placeholder options:0 completed:completedBlock];
}

- (void)sd_setImageWithURL:(nullable NSURL *)url
                  forState:(UIControlState)state
          placeholderImage:(nullable UIImage *)placeholder
                   options:(SDWebImageOptions)options
                 completed:(nullable SDExternalCompletionBlock)completedBlock {
    if (!url) {
        // 不传链接就移除掉指定状态对应的值
        [self.sd_imageURLStorage removeObjectForKey:imageURLKeyForState(state)];
    } else {
        // 根据指定状态保存链接
        self.sd_imageURLStorage[imageURLKeyForState(state)] = url;
    }
    
    // 调用UIView+WebCache分类方法加载图像
    __weak typeof(self)weakSelf = self;
    [self sd_internalSetImageWithURL:url
                    placeholderImage:placeholder
                             options:options
                        operationKey:imageOperationKeyForState(state)
                       setImageBlock:^(UIImage *image, NSData *imageData) {
                           [weakSelf setImage:image forState:state];
                       }
                            progress:nil
                           completed:completedBlock];
}

4.2.设置background image的方法实现

- (nullable NSURL *)sd_currentBackgroundImageURL {
    // 获取当前状态的背景图像地址
    NSURL *url = self.sd_imageURLStorage[backgroundImageURLKeyForState(self.state)];
    
    // 如果没有就获取普通状态的背景图像地址
    if (!url) {
        url = self.sd_imageURLStorage[backgroundImageURLKeyForState(UIControlStateNormal)];
    }
    
    return url;
}

- (nullable NSURL *)sd_backgroundImageURLForState:(UIControlState)state {
    // 获取指定状态的背景图像地址
    return self.sd_imageURLStorage[backgroundImageURLKeyForState(state)];
}

- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url forState:(UIControlState)state {
    // 调用全能方法
    [self sd_setBackgroundImageWithURL:url forState:state placeholderImage:nil options:0 completed:nil];
}

- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url forState:(UIControlState)state placeholderImage:(nullable UIImage *)placeholder {
    // 调用全能方法
    [self sd_setBackgroundImageWithURL:url forState:state placeholderImage:placeholder options:0 completed:nil];
}

- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url forState:(UIControlState)state placeholderImage:(nullable UIImage *)placeholder options:(SDWebImageOptions)options {
    // 调用全能方法
    [self sd_setBackgroundImageWithURL:url forState:state placeholderImage:placeholder options:options completed:nil];
}

- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url forState:(UIControlState)state completed:(nullable SDExternalCompletionBlock)completedBlock {
    // 调用全能方法
    [self sd_setBackgroundImageWithURL:url forState:state placeholderImage:nil options:0 completed:completedBlock];
}

- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url forState:(UIControlState)state placeholderImage:(nullable UIImage *)placeholder completed:(nullable SDExternalCompletionBlock)completedBlock {
    // 调用全能方法
    [self sd_setBackgroundImageWithURL:url forState:state placeholderImage:placeholder options:0 completed:completedBlock];
}

- (void)sd_setBackgroundImageWithURL:(nullable NSURL *)url
                            forState:(UIControlState)state
                    placeholderImage:(nullable UIImage *)placeholder
                             options:(SDWebImageOptions)options
                           completed:(nullable SDExternalCompletionBlock)completedBlock {
    if (!url) {
        // 不传链接就移除掉指定状态对应的值
        [self.sd_imageURLStorage removeObjectForKey:backgroundImageURLKeyForState(state)];
    } else {
        // 根据指定状态保存链接
        self.sd_imageURLStorage[backgroundImageURLKeyForState(state)] = url;
    }
    
    // 调用UIView+WebCache分类方法加载背景图像
    __weak typeof(self)weakSelf = self;
    [self sd_internalSetImageWithURL:url
                    placeholderImage:placeholder
                             options:options
                        operationKey:backgroundImageOperationKeyForState(state)
                       setImageBlock:^(UIImage *image, NSData *imageData) {
                           [weakSelf setBackgroundImage:image forState:state];
                       }
                            progress:nil
                           completed:completedBlock];
}

4.3.取消网络图像加载的方法实现

- (void)sd_cancelImageLoadForState:(UIControlState)state {
    // 取消指定key的图像加载操作
    [self sd_cancelImageLoadOperationWithKey:imageOperationKeyForState(state)];
}

- (void)sd_cancelBackgroundImageLoadForState:(UIControlState)state {
    // 取消指定key的背景图像加载操作
    [self sd_cancelImageLoadOperationWithKey:backgroundImageOperationKeyForState(state)];
}

源码阅读系列：SDWebImage

源码阅读：SDWebImage（一）——从使用入手

源码阅读：SDWebImage（二）——SDWebImageCompat

源码阅读：SDWebImage（三）——NSData+ImageContentType

源码阅读：SDWebImage（四）——SDWebImageCoder

源码阅读：SDWebImage（五）——SDWebImageFrame

源码阅读：SDWebImage（六）——SDWebImageCoderHelper

源码阅读：SDWebImage（七）——SDWebImageImageIOCoder

源码阅读：SDWebImage（八）——SDWebImageGIFCoder

源码阅读：SDWebImage（九）——SDWebImageCodersManager

源码阅读：SDWebImage（十）——SDImageCacheConfig

源码阅读：SDWebImage（十一）——SDImageCache

源码阅读：SDWebImage（十二）——SDWebImageDownloaderOperation

源码阅读：SDWebImage（十三）——SDWebImageDownloader

源码阅读：SDWebImage（十四）——SDWebImageManager

源码阅读：SDWebImage（十五）——SDWebImagePrefetcher

源码阅读：SDWebImage（十六）——SDWebImageTransition

源码阅读：SDWebImage（十七）——UIView+WebCacheOperation

源码阅读：SDWebImage（十八）——UIView+WebCache

源码阅读：SDWebImage（十九）——UIImage+ForceDecode/UIImage+GIF/UIImage+MultiFormat

源码阅读：SDWebImage（二十）——UIButton+WebCache

源码阅读：SDWebImage（二十一）——UIImageView+WebCache/UIImageView+HighlightedWebCache