NSURLSessionDataTask dataTaskWithURL完成处理程序未被调用 [英] NSURLSessionDataTask dataTaskWithURL completion handler not getting called

问题描述

我最近一直在学习Objective C，我决定尝试连接。

I have been learning Objective C lately, and I decided to try connections.

NSURLConnection的一切都很棒，直到我发现它已经过时，并试图工作与NSURLSession。

Everything was great with NSURLConnection, until I discovered it was outdated, and tried to work with NSURLSession.

我正在尝试一个非常简单的例子，但似乎无法让我的应用程序在完成块内运行代码。

I am trying a very simple example, but can't seem to get my app to run the code inside the completion block.

以下是使用的代码：

NSURL * url = [NSURL URLWithString:@"http://api.openweathermap.org/data/2.5/weather?q=London,uk"];

NSLog(@"2");
NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];
NSLog(@"3");

NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject
                                                             delegate: nil
                                                        delegateQueue: [NSOperationQueue mainQueue]];

NSLog(@"4");
NSURLSessionDataTask * dataTask = [defaultSession dataTaskWithURL:url
                                                completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
                                                    dispatch_sync(dispatch_get_main_queue(), ^{
                                                        NSLog(@"11");
                                                        if(error == nil)
                                                        {
                                                            NSString * text = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
                                                            NSLog(@"Data = %@",text);
                                                        }
                                                        NSLog(@"22");
                                                    });

                                                }];

NSLog(@"5");
[dataTask resume];
NSLog(@"6");

我得到主执行中打印的所有数字，但是从未执行completionHandler。我也尝试使用代表，但没有成功。

I get all the numbers printed from the main execution, but the completionHandler is never executed. I also tried this using a delegate, with no success.

提前致谢。

编辑
根据建议，我已将我的功能更改为以下内容：

EDIT As suggested, I have changed my function to the following:

-(void) doGET{
    NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration     defaultSessionConfiguration];
    NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject];
    NSURLSessionDataTask * dataTask = [defaultSession dataTaskWithURL:[self url]
                                                    completionHandler:^(NSData *data,    NSURLResponse *response, NSError *error) {
                                                            NSLog(@"11");
                                                            if(error == nil)
                                                            {
                                                                NSString * text = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
                                                                NSLog(@"Data = %@",text);
                                                            }
                                                            NSLog(@"22");

                                                    }];
    [dataTask resume];

}

我的完成经理仍未运行。我也尝试使用sharedSession而不是传递配置但也没有运气。

My completion manager is still not getting run. I also tried with the sharedSession instead of passing a configuration but no luck either.

感谢您的帮助

推荐答案

如果您打算使用数据任务的完成块再现，而不是指定的委托 > nil ，如下所示：

If you're going to use the completion block rendition of the data task, rather than specifying a delegate of nil, like this:

NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject
                                                             delegate: nil
                                                        delegateQueue: [NSOperationQueue mainQueue]];

您应该使用不带委托的方法来实例化您的会话：

NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject];

或者，假设您根本没有自定义配置，则可以跳过实例化完全 NSURLSessionConfiguration 并使用共享的 NSURLSession ：

Or, alternatively, given that you're not customizing your configuration at all, you can skip the instantiation of the NSURLSessionConfiguration altogether and use the shared NSURLSession:

NSURLSession *defaultSession = [NSURLSession sharedSession];

但是，底线，你不应该使用 sessionWithConfiguration：delegate：queue ： rendition除非你要实现委托，在这种情况下你不会使用 NSURLSessionDataTask 方法的再现c $ c> completionHandler 参数。

But, bottom line, you should not use the sessionWithConfiguration:delegate:queue: rendition unless you're going to implement the delegates, in which case you wouldn't use the rendition of the NSURLSessionDataTask method with the completionHandler parameter.

此外，请确保您的设备/模拟器运行iOS 7.0或更高版本。

Also, make sure your device/simulator is running iOS 7.0 or greater.

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