How to wait for asynchronous data before returning http.get

Question

I'm using ng2-ui-auth for my front-end and I've stumbled upon an issue I have no idea how to fix... This is a simple method from my UserService but there's a catch - an asynchronous method is being invoked to get one, necessary token for the http.get call.

getUser()
{
  const headers: Headers = new Headers();
  headers.append('Accept', 'application/json');
  headers.append('Content-Type', 'application/json');
  headers.append('X-Auth-Token', this.authService.getToken());

  const options = new RequestOptions({headers: headers});

  return this.http.get('http://localhost:9900/user', options).map(response => response.json());
}

The problem is - sometimes the http.get is being called before this.authService.getToken returns the data, so I end up with a null in 'X-Auth-Token', thus leaving me an 'Unauthorized' error.

Is there any way to wait until the header is complete and then return http.get?

I think this would have to be refactored so that getUser() itself returns a Promise. You'd place the authService call inside a Promise, with a then that executes the rest of your code. — Rob Zuber
– Rob Zuber, Commented Jun 26, 2017 at 0:27

Dody · Accepted Answer · 2017-06-25 23:47:54Z

1

Try using promises and method Then() to collect the response. Such like this:

getUser()
{
  const headers: Headers = new Headers();
  headers.append('Accept', 'application/json');
  headers.append('Content-Type', 'application/json');

  //Collect token value
  this.authService.getToken().then(function(resp){
      headers.append('X-Auth-Token', resp);
  });

  const options = new RequestOptions({headers: headers});

  return this.http.get('http://localhost:9900/user',options).map(response => response.json());
}

answered Jun 25, 2017 at 23:47

Dody

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2 Comments

Jakub Over a year ago

Thank you for your response. The problem is that this.authService.getToken() is of type String and therefore I can't use any methods such us subscribe, for instance. I'm trying to invoke getUser right after authorization with Facebook, and it seems that it takes a moment between logging in and AuthService to be ready to deliver data :/

Dody Over a year ago

hmmm, another approach is like you say, implement getUser after collect token AND wrap this authService.getToken method with some promise implementation. Is that method yours, right ?

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