ios - AFNetworking 2.0 完成下载多张图片

Question

我正在尝试找出一种使用 AFNewtorking 2.0 下载多个图像的方法。我在 SO 中阅读了很多帖子，但找不到我正在寻找的答案，希望你们能帮助我。

问题是我想知道所有下载何时完成以及是否所有图像都已下载。所以我有一个数组，其中包含图像 URL 的 Ant ，试图做这样的事情。

for(NSString *photoUrlString in self.photos){

        NSURL *url = [NSURL URLWithString:photoUrlString];
        AFHTTPRequestOperation *requestOperation = [[AFHTTPRequestOperation alloc] initWithRequest:[NSURLRequest requestWithURL:url]];
        requestOperation.responseSerializer = [AFImageResponseSerializer serializer];
        [requestOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {

        } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            NSLog(@"Image error: %@", error);
        }];
        [requestOperation start];
    }

通过将这些请求放入队列并将最大并发操作数设置为 1，我找到了一些答案。但不知道它是如何工作的。

感谢任何帮助，提前致谢!

Answer 1

for(Photo *photo in array){

    //form the path where you want to save your downloaded image to
    NSString *constPath = [photo imageFullPath];

    //url of your photo
    NSURL *url = [NSURL URLWithString:photo.serverPath];

    AFHTTPRequestOperation *op = [[AFHTTPRequestOperation alloc] initWithRequest:[NSURLRequest requestWithURL:url]];
    op.responseSerializer = [AFImageResponseSerializer serializer];

    op.outputStream = [NSOutputStream outputStreamToFileAtPath:constPath append:NO];
    op.queuePriority = NSOperationQueuePriorityLow;
    [op setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead){

    }];

    op.completionBlock = ^{

        //do whatever you want with the downloaded photo, it is stored in the path you create in constPath
    };
    [requestArray addObject:op];
}

NSArray *batches = [AFURLConnectionOperation batchOfRequestOperations:requestArray progressBlock:^(NSUInteger numberOfFinishedOperations, NSUInteger totalNumberOfOperations) {
} completionBlock:^(NSArray *operations) {

    //after all operations are completed this block is called
    if (successBlock)
        successBlock();
}];

[[NSOperationQueue mainQueue] addOperations:batches waitUntilFinished:NO];