angularjs - Angular & Firebase list not updating -

i'm new both angular & firebase. i've been trying create factory update list of stations list won't seem update. when run factory code firebase.database... in controller works fine though.

controller

.controller('dashctrl', function ($scope,stations) {          $scope.stations = [];         $scope.stations = stations.getstations();     }) 

services

.factory('stations', function() {     return {         getstations : function(){             firebase.database().ref('stations').once('value',function(snapshot){                 console.log(snapshot.val());                 return snapshot.val();             })         }     } }) 

what doing wrong? isn't ng-repeat="(key,station) in stations" list supposed change after factory returns new data ?

also i've been noticing in few tutorials. difference between below 2 inits.

.controller('dashctrl', function ($scope,stations) {          $scope.stations = [];         $scope.stations = stations.getstations();     })  .controller('dashctrl', [$scope,stations,function ($scope,stations) {          $scope.stations = [];         $scope.stations = stations.getstations();     }]) 

since didn't wrap firebase result angular promise, angular environment cannot notice there new results arrived, have 2 solutions:

1. using angular fire provide angular bindings firebase

2. wrap return result $q promise:

   //controller  .controller('dashctrl', function ($scope,stations) {     $scope.stations = [];     stations.getstations().then(function(results){         $scope.stations = results;     });  })  //service .factory('stations', function($q) {     return {         getstations : function(){             var defer = $q.defer();             firebase.database().ref('stations').once('value').then(function(snapshot){                 defer.resolve(snapshot.val());             }).catch(function(error){                 defer.reject(error);             })             return defer.promise;         }     } })