在IOS中使用Web服务时会发生NSURLSession内存泄漏

Question

我建立一个使用Web服务,以获得从Web服务我使用信息的应用NSURLSession和NSURLSessionDataTask.

我现在处于内存测试阶段,我发现它NSURLSession导致内存泄漏.

这不是所有泄漏.这就是我能够融入画面的一切.

以下是我如何设置NSURLSession并从Web服务请求信息.

#pragma mark - Getter Methods

- (NSURLSessionConfiguration *)sessionConfiguration
{
    if (_sessionConfiguration == nil)
    {
        _sessionConfiguration = [NSURLSessionConfiguration ephemeralSessionConfiguration];

        [_sessionConfiguration setHTTPAdditionalHeaders:@{@"Accept": @"application/json"}];

        _sessionConfiguration.timeoutIntervalForRequest = 60.0;
        _sessionConfiguration.timeoutIntervalForResource = 120.0;
        _sessionConfiguration.HTTPMaximumConnectionsPerHost = 1;
    }

    return _sessionConfiguration;
}

- (NSURLSession *)session
{
    if (_session == nil)
    {
        _session = [NSURLSession
                    sessionWithConfiguration:self.sessionConfiguration
                    delegate:self
                    delegateQueue:[NSOperationQueue mainQueue]];
    }

    return _session;
}

#pragma mark -


#pragma mark - Data Task

- (void)photoDataTaskWithRequest:(NSURLRequest *)theRequest
{

#ifdef DEBUG
    NSLog(@"[GPPhotoRequest] Photo Request Data Task Set");
#endif

    // Remove existing data, if any
    if (_photoData)
    {
        [self setPhotoData:nil];
    }

    self.photoDataTask = [self.session dataTaskWithRequest:theRequest];

    [self.photoDataTask resume];
}
#pragma mark -


#pragma mark - Session

- (void)beginPhotoRequestWithReference:(NSString *)aReference
{
#ifdef DEBUG
    NSLog(@"[GPPhotoRequest] Fetching Photo Data...");
#endif

    _photoReference = aReference;

    NSString * serviceURLString = [[NSString alloc] initWithFormat:@"%@/json?photoreference=%@", PhotoRequestBaseAPIURL, self.photoReference];

    NSString * encodedServiceURLString = [serviceURLString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

    serviceURLString = nil;

    NSURL * serviceURL = [[NSURL alloc] initWithString:encodedServiceURLString];

    encodedServiceURLString = nil;

    NSURLRequest * request = [[NSURLRequest alloc] initWithURL:serviceURL];

    [self photoDataTaskWithRequest:request];

    serviceURL = nil;
    request = nil;
}

- (void)cleanupSession
{
#ifdef DEBUG
    NSLog(@"[GPPhotoRequest] Session Cleaned Up");
#endif

    [self setPhotoData:nil];
    [self setPhotoDataTask:nil];
    [self setSession:nil];
}

- (void)endSessionAndCancelTasks
{
    if (_session)
    {
#ifdef DEBUG
        NSLog(@"[GPPhotoRequest] Session Ended and Tasks Cancelled");
#endif

        [self.session invalidateAndCancel];

        [self cleanupSession];
    }
}

#pragma mark -


#pragma mark - NSURLSession Delegate Methods

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
#ifdef DEBUG
    NSLog(@"[GPPhotoRequest] Session Completed");
#endif

    if (error)
    {
#ifdef DEBUG
        NSLog(@"[GPPhotoRequest] Photo Request Fetch: %@", [error description]);
#endif

        [self endSessionAndCancelTasks];

        switch (error.code)
        {
            case NSURLErrorTimedOut:
            {
                // Post notification
                [[NSNotificationCenter defaultCenter] postNotificationName:@"RequestTimedOut" object:self];
            }
                break;

            case NSURLErrorCancelled:
            {
                // Post notification
                [[NSNotificationCenter defaultCenter] postNotificationName:@"RequestCancelled" object:self];
            }
                break;

            case NSURLErrorNotConnectedToInternet:
            {
                // Post notification
                [[NSNotificationCenter defaultCenter] postNotificationName:@"NotConnectedToInternet" object:self];
            }
                break;

            case NSURLErrorNetworkConnectionLost:
            {
                // Post notification
                [[NSNotificationCenter defaultCenter] postNotificationName:@"NetworkConnectionLost" object:self];
            }
                break;

            default:
            {

            }
                break;
        }
    }
    else {

        if ([task isEqual:_photoDataTask])
        {
            [self parseData:self.photoData fromTask:task];
        }
    }
}

- (void)URLSession:(NSURLSession *)session didBecomeInvalidWithError:(NSError *)error
{
    if (error)
    {

#ifdef DEBUG
        NSLog(@"[GPPhotoRequest] Session Invalidation: %@", [error description]);
#endif

    }

    if ([session isEqual:_session])
    {
        [self endSessionAndCancelTasks];
    }
}

#pragma mark -


#pragma mark - NSURLSessionDataTask Delegate Methods

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{

#ifdef DEBUG
    NSLog(@"[GPPhotoRequest] Received Data");
#endif

    if ([dataTask isEqual:_photoDataTask])
    {
        [self.photoData appendData:data];
    }
}

#pragma mark -

问题: 为什么NSURLSession导致这些内存泄漏？NSURLSession当我完成它时,我无效.我还发布了我不需要的任何属性,并将会话设置为nil(请参阅 - (void)cleanupSession& - (void)endSessionAndCancelTask​​s).

其他信息: 会话完成并"清理"后会发生内存泄漏.有时,它们也会在我弹出之后发生UIViewController.但是,我的所有自定义(GPPhotoRequest和GPSearch)对象和UIViewController都被释放(我通过添加NSLog确保).

我尽量不发布很多代码,但我觉得大部分都需要被看到.

如果您需要更多信息,请与我们联系.非常感谢帮助.

Answer 1

当我切换到NSURLSession时,我有同样的"漏洞",内存管理问题.对我来说,在创建会话并恢复/启动dataTask之后,我从未告诉会话自我清理(即释放分配给它的内存).

// Ending my request method with only the following line causes memory leaks
[dataTask resume];

// Adding this line fixed my memory management issues
[session finishTasksAndInvalidate];

来自文档:

在最后一个任务完成并且会话进行最后一次委托调用之后,对委托和回调对象的引用被破坏.

清理我的会话修复了通过Instruments报告的内存泄漏.

Answer 2

重新阅读URL 加载系统编程指南后发现我NSURLSession太早将该属性设置为 nil 了。

相反，我需要NSURLSession在收到委托消息后将该属性设置为 nil URLSession:(NSURLSession *)session didBecomeInvalidWithError:(NSError *)error，这是有道理的。幸运的是，这是一个小错误。

例如

- (void)URLSession:(NSURLSession *)session didBecomeInvalidWithError:(NSError *)error
{
    if (error)
    {

#ifdef DEBUG
        NSLog(@"[GPPhotoRequest] Session Invalidation: %@", [error description]);
#endif

    }

    if ([session isEqual:_session])
    {
        [self cleanupSession];
    }
}