循环中多个请求的nsurlsession

Question

如果url正确，我在调试导航器中看不到任何队列，因为它没有再次调用方法。我在networking库中引用了相同的内容，但我想它的工作方式与我在NSURLSession中的工作方式相同，对吗？

案例：-我检查url是否存在，所以如果存在，就加载两个url(time.txt和image.png)，否则调用WebService(XmlParser)&保留以下文件的url检查。

time.txt+image.png 

or 

tryagain.txt

显示哪个存在。

-(void)downloading
{
 NSString *imageUrl = [NSString stringWithFormat:@"%@",txtNumber.text];
       
 NSURLSessionConfiguration *sessionConfig =[NSURLSessionConfiguration defaultSessionConfiguration];
        
 NSURLSession *session =[NSURLSession sessionWithConfiguration:sessionConfig
                                               delegate:self
                                          delegateQueue:nil];
        
 NSURLSessionDownloadTask *getImageTask = [session downloadTaskWithURL:[NSURL URLWithString:imageUrl]
                        
                                  completionHandler:^(NSURL *location,
                                                      NSURLResponse *response,
                                                      NSError *error)
                        {
                           UIImage *downloadedImage =[UIImage imageWithData:[NSData dataWithContentsOfURL:location]];

                                      dispatch_async(dispatch_get_main_queue(), ^{
                                          // do stuff with image
                                          if (downloadedImage)
                                          {
                                              carImgView.image = downloadedImage;
                                              result = TRUE;
                                          }
                                          else
                                          {
                                              result = FALSE;
                                              [self tryagain];
                                          }
                                      });
                                  }];
        
        [getImageTask resume];
}

-(void)tryagain
{
    NSString *strImg = [[NSString stringWithFormat:@"%@",gblPolicyNo] stringByAppendingString:FilePolStatus];
    
    NSString *apiImage = [NSString stringWithFormat:@"http://moviepoint.info/%@/%@",FolderPolStatus,strImg];
    
    NSURL *aImgUrl = [NSURL URLWithString:apiImage];
    // 2
    NSURLSessionConfiguration *sessionConfig =
    [NSURLSessionConfiguration defaultSessionConfiguration];
    
    // 3
    tryAgainSession =[NSURLSession sessionWithConfiguration:sessionConfig
                                           delegate:self
                                      delegateQueue:nil];
    
    
    // 1
    getTryAgainTask = [tryAgainSession downloadTaskWithURL:aImgUrl
                    
                    
                              completionHandler:^(NSURL *location,
                                                  NSURLResponse *response,
                                                  NSError *error)
                    {
                        
                        // 2
                        UIImage *downloadedImage =[UIImage imageWithData:[NSData dataWithContentsOfURL:location]];
                        //3
                        dispatch_async(dispatch_get_main_queue(), ^{
                            // do stuff with image
                            if (downloadedImage)
                            {
                                [policyImgWebView loadData:[NSData dataWithContentsOfURL:location] MIMEType:nil textEncodingName:nil baseURL:nil];
                                NSLog(@"YES");
                            }
                            else
                            {
                                NSLog(@"NO");
                                [self performInBackground];
                            }
                        });
                    }];
    
    // 4
    [getTryAgainTask resume];
    
}

Answer 1

通过获取一个全局NSURLSession解决