iOS setCompletionBlock 异步请求

__weak ASIHTTPRequest *request = [ASIHTTPRequestrequestWithURL:url];

   __blockNSString *jsonStr = [[NSStringalloc]init];

    __blockNSDictionary *dic= [[NSDictionaryalloc]init];

    [request setCompletionBlock:^{

      // 请求成功后，再此接收返回数据

        }];

    

    [request startAsynchronous];