Angular promise in more controllers

Question

I'm defining a factory using promises like:

.factory('Test', ['$q', '$http', function ($q, $http){
     var getData = function () {
         var deferred = $q.defer();
         $http.get('url')
              .success(function (res) {
                   deferred.resolve(res);
              });

         return deferred.promise;
     }

     return { getData: getData};
}]);

Further in a controller I'm using that factory like:

Test.getData().then(function (data) { console.log(data);});

All works fine, my question is: if I want to use the same promise in another controller to wait for that ajax before I do something else, I should use the same sintax?

Test.getData().then(function (data) { console.log(data);});

My problem is that I'm using a node js socket to retreive some data and events. In my promise I'm connecting the socket

$rootScope.socket = io_connection

and in another controller, on anther page I want to emit an event on that socket but $rootScope.socket gets undefined. Since $rootScope.socket gets defined in that first promise, in my other controller I tried:

$rootScope.socket.emit('custom_event', { id: 1 });

But is undefined... I hope my writing makes sense. Thanks

maybe you should show the code where you initialize the socket and the controller where you wanna emit an event. You should create the socket in the run phase. - BTW `$http` returns already a promise, there is no need to wrap another layer around it. — Michael, Sep 28 '15 at 12:12
I made that promise after an example of how to use promises in angular... I will post the code, thanks — Iulian Miu, Sep 28 '15 at 12:18
?? Then I'd look for better examples or for examples with a proper explanation. It might be just an example, but in this scenario it doesn't make sense :-) — Michael, Sep 28 '15 at 12:21
Avoid the [deferred antipattern](http://stackoverflow.com/q/23803743/1048572)! — Bergi, Sep 28 '15 at 12:50
[link](https://jsfiddle.net/bxbq8j9z/) here's a part of the code that uses socket — Iulian Miu, Sep 28 '15 at 13:02

score 1 · Accepted Answer · answered Sep 29 '15 at 01:59

since your getData always returns a promise, instead of holding the actual data, you can hold the promise object instead:

.factory('LoggedUserData', ['$q', '$http', function ($q, $http) {
    var waitingPromise = null;

    var getData = function () {
        if(!waitingPromise){
            waitingPromise = $http.get('url');
        }
        return waitingPromise;;
    }
    return { getData: getData };
}])

now, irrespective of which controller object gets initaized first, both would recieve the same data.

score 0 · Answer 2 · answered Sep 28 '15 at 12:11

You need to define witch controller is instantiated first.

I don't know if is a good idea to make controllers dependent on each other if they don't have scope inheritance.

Maybe you can create this socket inside a Service and use on both controllers.

Angular promise in more controllers

2 Answers2