ios - 不调用 NSURLSessionDataTask 委托(delegate)方法

Question

我正在尝试从 API 下载一些 JSON。现在什么都没有打印出来。

我确信路径和 API Key/Value 有效，因为我是通过带有完成处理程序的 NSURLSessionDataTask 完成的，但我想了解如何使用委托(delegate)方法执行相同的操作。

但我似乎无法弄清楚为什么我的委托(delegate)方法没有被调用。

@interface MetaData () <NSURLSessionDelegate, NSURLSessionDataDelegate>

@end

@implementation MetaData
-(void)downloadData
{
    NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];

    [sessionConfig setHTTPAdditionalHeaders:@{ header : key}];
    NSURLSession *defaultSesh = [NSURLSession sessionWithConfiguration:sessionConfig];
    NSURLSessionDataTask *dataTask = [defaultSesh dataTaskWithURL:[NSURL URLWithString:path]];
    defaultSesh = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];
    [dataTask resume];


}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
{
    NSLog(@"here 2");
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{
    NSLog(@"here");
    _weaponDictionary = [NSJSONSerialization JSONObjectWithData:data
                                                        options:kNilOptions
                                                          error:nil];
    NSLog(@"dictionary: %@", _weaponDictionary);
}

感谢您的帮助。

编辑

defaultSesh = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];

通过添加该行，我将委托(delegate)设置为自己。所以现在我打印“here 2”但仍然不打印字典...

Answer 1

使用方法

+ (NSURLSession *)sessionWithConfiguration:(NSURLSessionConfiguration *)configuration
                                  delegate:(id<NSURLSessionDelegate>)delegate
                             delegateQueue:(NSOperationQueue *)queue

正确设置委托(delegate)。

更新:

而且你必须调用didReceiveResponse的完成处理程序

completionHandler

A completion handler that your code calls to continue the transfer, passing a constant to indicate whether the transfer should continue as a data task or should become a download task.
• If you pass NSURLSessionResponseAllow, the task continues normally.
• If you pass NSURLSessionResponseCancel, the task is canceled.
• If you pass NSURLSessionResponseBecomeDownload as the disposition, your delegate’s URLSession:dataTask:didBecomeDownloadTask: method is called to provide you with the new download task that supersedes the current task.

例如

- (void) URLSession:(NSURLSession *)session 
           dataTask:(NSURLSessionDataTask *)dataTask 
 didReceiveResponse:(NSURLResponse *)response 
  completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
    completionHandler(NSURLSessionResponseAllow);
}