AFHTTPRequestOperation获取responseObject

Question

@property (nonatomic, strong) NSDictionary *dic;

#pragma mark - 从网络获取json数据

• (NSDictionary *)getJsonData{

  NSString *urlStr = @"http://api.worldweatheronline.com/free/v2/weather.ashx?q=chengdu&num_of_days=7&format=json&tp=6&key=5fc3a5873e9bdb5bbf8116ea3aac5";
  NSURL *url = [NSURL URLWithString:urlStr];
  NSURLRequest *request = [NSURLRequest requestWithURL:url];

  //使用AFNetworking解析json数据
  //实例化http操作请求
  AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];

  //设定解析器
  operation.responseSerializer = [AFJSONResponseSerializer serializer];

  //下载数据并解析
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

  [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
  
      //json数据全局化
      self.dic = (NSDictionary *)responseObject;
  
  } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
      NSLog(@"解析出错：%@",error);
  }];
  

  });
  [operation start];

  return self.dic;
  }
  我已经提升dic成属性了，为什么返回的self.dic为空？
  个人猜想是跟 block 执行时期有关，希望能有人指点迷津，谢谢！

Answer 1

你这是创建一个分线程去下载数据，但是下载完成后没有刷新主线程。你这边返回的self.dic是肯定是空得。应该是下载完成（下载成功或者失败都是完成）后再返回dic，这才比较合理。