使用委托，操作和队列 [英] Using delegates, operations, and queues

问题描述

我使用的是 AWS SDK 的iOS上传和下载文件，并从当地硬盘驱动器到Amazon S3存储。我有能力做这项工作，但我无法得到S3代表回应时正确操作完成后，或产生错误来提醒我。

I am using the AWS SDK for iOS to upload and download files to and from local hard drive to Amazon S3 storage. I am capable of making this work but I am unable to get the S3 delegate to respond properly to alert me when operations have finished or resulted in an error.

我有我要上传文件的数组。对于每一个文件创建一个的NSOperation 其中主程序由大量的：

I have an array of files that I want to upload. For each file I create a NSOperation where the main routine consist mostly of:

    AmazonCredentials * credentials = [[AmazonCredentials alloc] initWithAccessKey:ACCESS_KEY_ID withSecretKey:SECRET_KEY];
    putObjectRequest = [[S3PutObjectRequest alloc] initWithKey:pathCopy inBucket:[self bucket]];
    putObjectRequest.filename = pathSource;
    putObjectRequest.credentials=credentials;
    [putObjectRequest setDelegate:s3Delegate];

下面，委托（ s3Delegate ）是一个普通的<创建的href="http://docs.amazonwebservices.com/AWSiOSSDK/latest/protocol_amazon_service_request_delegate-p.html"相对=nofollow> AmazonServiceRequestDelegate 的哪些应该能够断火的响应时的动作已完成。每一个我的 NSOperations 添加到我的 NSOperationQueue 其中执行操作不兼任。如果我使用代理 [putObjectRequest setDelegate：s3Delegate] 的操作无法正常工作。如果删除了使用委托的操作都正确执行，但我无法得到任何回复的操作，因为我没有一个代表。

Here, the delegate (s3Delegate) is created as a regular AmazonServiceRequestDelegate which should be able to fire off responses when an operation has finished. Each of my NSOperations are added to my NSOperationQueue which executes operations non-concurrently. If I use the delegate [putObjectRequest setDelegate:s3Delegate] the operations are not working. If I remove the use of the delegate the operations are performed correctly but I am unable to receive any responses to the operations as I do not have a delegate.

如果我删除了使用 NSOperationQueue 完全并使用 [putObjectRequest setDelegate：s3Delegate] 的代表作品完美。

If I remove the use of the NSOperationQueue completely and use the [putObjectRequest setDelegate:s3Delegate] the delegate works perfectly.

我的问题是我在做什么错用为代表的队列？由于委托是完全有能力执行而不是在一个队列会这样涉及到不执行​​主线程上的？我真的希望能够使用队列来限制非并发操作数，但是我无法想出解决办法。我希望有人有什么是怎么回事的想法，任何例如code会大大AP preciated。谢谢！ 欢呼声中，特龙

My question is what am I doing wrong with using a delegate in a queue? Since the delegate is perfectly capable of performing while not in a queue could this be related to not performing on the main thread? I really want to be able to use the queue to limit the number of non-concurrent operations, however I am unable to figure this out. I hope someone has an idea of what is going on here and any example code would be greatly appreciated. Thanks! Cheers, Trond

推荐答案

看来，AWS SDK您设置的委托时间之后的行为是异步的。 因此，为了让您的异步AWS的东西的工作中（异步）的NSOperation，你得把一些魔法等待AWS来完成：

It seems that the aws sdk behaves asynchronously after the time you set your delegate. So in order to have your asynchronous aws stuff work in a (asynchronous) NSOperation, you got to put some magic to wait for AWS to complete:

在您的.H的NSOperation文件，添加一个布尔值：

In your .h NSOperation file, add a boolean:

@interface UploadOperation : NSOperation <AmazonServiceRequestDelegate> {
    @private
    BOOL        _doneUploadingToS3;
}

和你的.m文件，你的主要方法是这样的：

and in your .m file, your main method will look like this:

- (void) main
{   
    ....  do your stuff …..

    _doneUploadingToS3 = NO;

    S3PutObjectRequest *por = nil;
    AmazonS3Client *s3Client = [[AmazonS3Client alloc] initWithAccessKey:ACCESS_KEY withSecretKey:SECRET_KEY];
    s3Client.endpoint = endpoint;

    @try {
        por = [[[S3PutObjectRequest alloc] initWithKey:KEY inBucket:BUCKET] autorelease];
        por.delegate = self;
        por.contentType = @"image/jpeg";
        por.data = _imageData;

        [s3Client putObject:por];
    }
    @catch (AmazonClientException *exception) {
        _doneUploadingToS3 = YES;
    }

    do {
        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    } while (!_doneUploadingToS3);

    por.delegate = nil;

    ....  continue with your stuff ….
}

不要忘记实现你的委托方法

do not forget to implement your delegate methods

-(void)request:(AmazonServiceRequest *)request didCompleteWithResponse:(AmazonServiceResponse *)response
{
    _doneUploadingToS3 = YES;
}

-(void)request:(AmazonServiceRequest *)request didFailWithError:(NSError *)error 
{
    _doneUploadingToS3 = YES;
}

-(void)request:(AmazonServiceRequest *)request didFailWithServiceException:(NSException *)exception 
{
    _doneUploadingToS3 = YES;
}

- (void) request:(AmazonServiceRequest *)request didSendData:(NSInteger)bytesWritten totalBytesWritten:(NSInteger)totalBytesWritten totalBytesExpectedToWrite:(NSInteger)totalBytesExpectedToWrite
{
    // Do what you want
}

-(void)request:(AmazonServiceRequest *)request didReceiveResponse:(NSURLResponse *)response
{
    // Do what you want
}

-(void)request:(AmazonServiceRequest *)request didReceiveData:(NSData *)data
{
    // Do what you want
}

注意：这个魔术可以为异步执行任何东西，工作，但在一个的NSOperation实施

Note: this magic can work for any stuff that performs asynchronously but have to be implemented in a NSOperation.

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