ios - 如何返回方法的输出是使用 NSURLConnection 异步调用 block

Question

我正在向服务器发送请求以使用 NSURLConnection block 方法获得响应。我无法在 block 中使用 return YES 或 return NO。我该如何解决这个问题？

-(BOOL)checkForValidUrl:(NSString *)url
{
       __block int httpStatus=0;
        NSMutableURLRequest *request=[[NSMutableURLRequest alloc]initWithURL:[NSURL URLWithString:url]];
        [request setValue:@"application/json" forHTTPHeaderField:@"content-type"];
        [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];


        [NSURLConnection sendAsynchronousRequest:request
                                           queue:[NSOperationQueue mainQueue]
                               completionHandler:^(NSURLResponse *response, NSData *responseData, NSError *error)
         {
            httpStatus = [((NSHTTPURLResponse *)response) statusCode];
             NSLog(@"httpStatus inside block:%d",httpStatus);


         }
         ];

        return NO;
}

Answer 1

不返回任何东西，而是传递一个完成 block ，稍后将检查结果通知调用者。您将不得不重新编写调用代码，以便不需要立即得到结果。

例如，假设 200 响应意味着 URL 有效:

-(void)checkForValidUrl:(NSString *)url completion:(void (^)(BOOL validURL))completion {
  __block int httpStatus=0;
  NSMutableURLRequest *request=[[NSMutableURLRequest alloc]initWithURL:[NSURL URLWithString:url]];
  [request setValue:@"application/json" forHTTPHeaderField:@"content-type"];
  [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];


  [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue]
    completionHandler:^(NSURLResponse *response, NSData *responseData, NSError *error) {
      httpStatus = [((NSHTTPURLResponse *)response) statusCode];
      NSLog(@"httpStatus inside block:%d",httpStatus);

      completion(200 == httpStatus);
    }
  ];
}