sdwebimage在下载图片之前为什么要先取消之前的操作？

Question

- (void)sd_setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholder options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletionBlock)completedBlock {
    [self sd_cancelCurrentImageLoad];
    objc_setAssociatedObject(self, &imageURLKey, url, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

    if (!(options & SDWebImageDelayPlaceholder)) {
        dispatch_main_async_safe(^{
            self.image = placeholder;
        });
    }

为什么要做[self sd_cancelCurrentImageLoad];这个操作？

Answer 1

针对一个UIImageView，肯定要取消前一个操作，省时、省流量