Angular factory returning a promise

$http itself return promise you don’t need to bind it inside the $q this is not a good practice and considered as Anti Pattern.

Use:-

    app.factory('settings', ['$rootScope', '$http', '$q', function($rootScope, $http) {
        return $http.get('/api/public/settings/get')
    }]);

    app.controller('SomeCtrl', ['settings',$scope, function(settings,$scope) {
        settings.then(function(result){
                $scope.settings=result.data;
          });
    }]);

Your way can be done as :-

app.factory('settings', ['$rootScope', '$http', '$q', function($rootScope, $http, $q) {
    var deferred = $q.defer();

    $http.get('/api/public/settings/get').success(function(data) {
        deferred.resolve(data);
    });

    return deferred.promise;
}]);

app.controller('SomeCtrl', ['$scope', 'settings', function($scope, settings) {
    settings.then(function(data){
          $scope.settings=data;
       })
}]);

Don’t overload $rootScope if you wanted it you need to use $watch for the changes in $rootScope(Not recommended).