如何在AngularJS中更新父作用域

我试图使用两个解决方案从子控制器更新我的父范围，但我不能使它工作。apply()不工作

HTML:

<div ng-controller="ControllerA">
   <div ng-show="tab_selected == 1">Content1</div>
   <div ng-show="tab_selected == 2">Content2</div>
   <div ng-controller="ControllerB">
      <span ng-click="updateScope()"></span>
   </div>
</div>

app.controller('ControllerA', ['$scope', 
  function ($scope) {
     $scope.tab_selected = 1;
}]);
app.controller('ControllerB', ['$scope', 
  function ($scope) {
     $scope.updateScope = function(){
        $scope.tab_selected = 2;
        // $scope.apply(function(){  $scope.tab_selected = 2; }); 
     }
}]);