Downloading JSON file using NSURLSession.

gistfile1.m

// Create a sample URL.
    NSURL *url = [NSURL URLWithString:@"http://www.bbc.co.uk/tv/programmes/genres/drama/scifiandfantasy/schedules/upcoming.json"];
    
    // Create a download task.
    NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:url
                                                             completionHandler:^(NSData *data,
                                                                                 NSURLResponse *response,
                                                                                 NSError *error)
                                  {
                                      if (!error)
                                      {
                                          NSError *JSONError = nil;
                                          
                                          NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data
                                                                                                     options:0
                                                                                                       error:&JSONError];
                                          if (JSONError)
                                          {
                                              NSLog(@"Serialization error: %@", JSONError.localizedDescription);
                                          }
                                          else
                                          {
                                              NSLog(@"Response: %@", dictionary);
                                          }
                                      }
                                      else
                                      {
                                          NSLog(@"Error: %@", error.localizedDescription);
                                      }
                                  }];
    // Start the task.
    [task resume];