废话不多说，直接上问题：
1.如何拼接请求头？

//申明返回的结果是json类型
  
  manager.responseSerializer = [AFJSONResponseSerializer serializer];
  
  //申明请求的数据是json类型
  
  manager.requestSerializer=[AFJSONRequestSerializer serializer];
  
  //  /如果报接受类型不一致请替换一致text/html或别的
  
  [manager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Accept"];
  [manager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
  [manager.requestSerializer setValue:value forHTTPHeaderField:key];
  [manager.requestSerializer setValue: value forHTTPHeaderField:key];
  [manager.requestSerializer setValue: value forHTTPHeaderField:key];
  

2.如何返回参数在调用的同一方法中？

block,参数带有block去实现

__block NSString *longitude; // __block,静态变量
[self.manager POST:URL parameters:params success:^(NSURLSessionDataTask * _Nonnull task, id  _Nonnull responseObject) {
  
  NSDictionary *locDictionary = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingMutableLeaves error:nil];
  longitude = [locDictionary objectForKey:@"lon"]; // 纠正后经度
  
  if (finishBlock)
  {
    finishBlock(longitude, nil);
  }
  
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
  NSLog(@"%@", error);
  if (finishBlock)
  {
    finishBlock(nil, error);
  }
}];