Create promise in AngularJS

Question

I'm trying to create a promise in Angular with the $q service. It returns an object retrieved from a web service. If the object is in the cache, it returns it without calling the web service.

The problem is that the two resolves are getting called.

Maybe, Am I using a promise anti-pattern?

Here is my code:

    function returnMapAsync() {

  return $q(function (resolve, reject) {
    if (navigationMap) {
      resolve(navigationMap);
    } else {
      ServerRequest.getNavigationMap().then(function (data) {
        navigationMap = data.object;
        resolve(navigationMap);
      });
    }
  });
}

Thank you

Yes you are - good that you've asked :-)

Bergi
– Bergi

2015-06-24 10:29:24 +00:00
Commented Jun 24, 2015 at 10:29 — Bergi
– Bergi, Commented Jun 24, 2015 at 10:29
see also How to return an object in my case?

Bergi
– Bergi

2015-06-24 10:34:37 +00:00
Commented Jun 24, 2015 at 10:34 — Bergi
– Bergi, Commented Jun 24, 2015 at 10:34

Davin Tryon · Accepted Answer · 2015-06-24 10:25:58Z

3

You shouldn't need to wrap everything in the $q() call. In order to promisify navigationMap use $q.when:

function returnMapAsync() {

    if (navigationMap) {
        return $q.when(navigationMap);
    }
    return ServerRequest.getNavigationMap();
}

answered Jun 24, 2015 at 10:25

Davin Tryon

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Comments

dfsq · Accepted Answer · 2015-06-24 10:33:35Z

2

You don't need to wrap it into one more promise since ServerRequest.getNavigationMap() is a promise:

function returnMapAsync() {

    if (navigationMap) {
        return $q.resolve(navigationMap);
    } 

    return ServerRequest.getNavigationMap().then(function(data) {
        navigationMap = data.object;
        return navigationMap;
    });
}

answered Jun 24, 2015 at 10:33

dfsq

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