ios - NSURLSession的内存泄漏

Question

在xcode仪器中，我遇到此方法内存泄漏

- (void)getDataForRequest:(NSURLRequest *)request completionHandler:(downloadCompletionBlock)completionHandler
{
    self.expectedLength = 0;
    self.currentLength = 0;
    self.responseData = Nil;
    
    self.contentLengthBlock = nil;
    self.completionBlock = completionHandler;
    
    NSURLSession *session = [NSURLSession sharedSession];
    
    NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
    
    session = [NSURLSession sessionWithConfiguration:defaultConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]];
    
    self.postDataTask = [session dataTaskWithRequest:request];
    
    [self.postDataTask resume];
}

Answer 1

此代码段中的问题是，您正在为每个请求创建一个新的NSURLSession，并且您永远不会使 session 无效。如果在请求启动后调用finishTasksAndInvalidate，它将:

请求完成时，

回收与NSURLSession相关的内存；这样，它也会

释放对delegate对象的强引用。

从而:

- (void)getDataForRequest:(NSURLRequest *)request completionHandler:(DownloadCompletionBlock)completionHandler {
    self.expectedLength = 0;
    self.currentLength = 0;
    self.responseData = nil;

    self.contentLengthBlock = nil;
    self.completionBlock = completionHandler;

    NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:defaultConfigObject delegate:self delegateQueue:[NSOperationQueue mainQueue]];

    self.postDataTask = [session dataTaskWithRequest:request];

    [self.postDataTask resume];
    [session finishTasksAndInvalidate];
}

如果您不使用finishTasksAndInvalidate，则会看到类似这样的泄漏:

调用finishTasksAndInvalidate将解决这些问题。