ios - 等待 block 完成吗？

Question

是否可以等待某些服务器查询块结束其操作？我的无效代码如下；

 + (BOOL) loginQueryFromServer:(NSDictionary *)parameters{

  __block BOOL loginQueryResult = NO;

  AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

  AFHTTPRequestOperation *operation = [manager POST:@"http://domainname/login/" parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {

    NSLog(@"Response1: %@",responseObject);
    loginQueryResult = YES;
    NSLog(@"Response2: %@", loginQueryResult ? @"YES" : @"NO");
  } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

    NSLog(@"Error: %@", error);
    loginQueryResult = NO;
  }];
  [operation start];
  [operation waitUntilFinished];

  NSLog(@"Response3: %@", loginQueryResult ? @"YES" : @"NO");
  return loginQueryResult;
}

结果:(如您所见； Response3首先记录)

2014-04-09 21:11:17.072 aaa[1010:70b] Response3: NO
2014-04-09 21:11:17.073 aaa[1010:70b] Response1: {
    reply = "Login successful!";
}
2014-04-09 21:11:17.081 aaa[1010:70b] Response2: YES

Answer 1

我知道这并不能完全回答问题-但我建议您重写loginQueryFromServer:方法以接受完成块本身，以便它是异步的(我认为这最终是您想要做的事情):

+ (void) loginQueryFromServer:(NSDictionary *)parameters completion:(void(^)(BOOL response, NSError *error))completionBlock {

    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

    AFHTTPRequestOperation *operation = [manager POST:@"http://domainname/login/" parameters:parameters success:^(AFHTTPRequestOperation *operation, id responseObject) {

        completionBlock(YES, nil);

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        completionBlock(NO, error);
    }];
    [operation start];
} 

像这样使用它:

[YourClass loginQueryFromServer:someDictionary completion:^(BOOL response, NSError *error) {

    // do something with the response and the error if it exists
}];