angular controller as watch variable in parent controller

how do i watch a variable, that is bind to a parent controller?

function config($stateProvider) {
    $stateProvider
        .state('home', {
            url: '/',
            templateUrl: 'home.html',
            controller: 'HomeController',
            controllerAs: 'vm'
        })

        .state('home.child', {
            url: '/child',
            templateUrl: 'child.html',
            controller: 'ChildController',
            controllerAs: 'vm'
        });
}

function HomeController($scope) {
    this.title = 'Some Title';
}

function ChildController($scope) {
    var vm = this;
    $scope.$watch('vm.title', function(current, original) {
        $log.info('title was %s', original);
        $log.info('title is now %s', current);
    });

}

The watch-Function doesn't recognize changes on the parent title..

thanks! :)

Solution

Just access the $parent scope when referencing objects belonging to the parent. Also get used to a cleaner and more standardized way of structuring your controller JS.

HTML

<html ng-app="myApp">
  <body>
    <div ng-controller="HomeController">
      <input type="text" ng-model="title">
      <div ng-controller="ChildController"></div>
    </div>
  </body>
</html>

var app = angular.module("myApp", []);
app.controller("HomeController", ['$scope', '$log', function ($scope, $log) {
  $scope.title = "Some Title";
}]);

app.controller("ChildController", ['$scope', '$log', function ($scope, $log){
  $scope.$watch('$parent.title', function(newValue, oldValue) {
    $log.info('title was %s', oldValue);
    $log.info('title is now %s', newValue);
  });
}]);