SDWebImage-SDWebImageDownloader下載圖片

[[SDWebImageDownloader sharedDownloader] downloadImageWithURL:[NSURL URLWithString:imgUrl] options:SDWebImageDownloaderHighPriority progress:nil completed:^(UIImage *image, NSData *data, NSError *error, BOOL finished) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    if (wkself) {
                        wkself.thumbImage = image;
                    }
                });
            }];