有关UIImageView+AFNetworking 下载图片的线程问题

 NSString *urlstring=[dict objectForKey:@"imagePath"];
    NSURL *url=[NSURL URLWithString:urlstring];//获取图片的url路径
    NSURLRequest *urlrequest=[[NSURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:10];
    NSLog(@"UI Thread is %@",[NSThread currentThread]);//这里是主线程
    //使用UIImageView+AFNetWorking 异步下载图片，缓存到本地
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
         NSLog(@"current Thread :%@",[NSThread currentThread]);//这里使用异步机制，肯定是非UI线程
        [cell.myImage setImageWithURLRequest:urlrequest
                            placeholderImage:[UIImage imageNamed:[dict objectForKey:@"imageName"]]
                                     success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
            NSLog(@"load image thread is %@",[NSThread currentThread]);//猜猜这里是什么线程？？
            dispatch_async(dispatch_get_main_queue(), ^{
                cell.myImage.image=image;
                 NSLog(@"image thread :%@",[NSThread currentThread]);//这里肯定是主线程
            });
           
            NSLog(@"下载图片成功");
        } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
            NSLog(@"图片加载失败:%@",error);
        }];