问从我的指令中，如何手动触发父作用域上的摘要周期？

EN

<div ng-app='app'>
  <one></one>
  <two></two>
</div>

angular
  .module('app', [])
  .directive('one', function() {
    return {
      restrict: 'E',
      scope: {},
      template: "<input ng-model='shared.val'> {{ shared.val }}",
      controller: function($scope, Shared) {
        $scope.shared = Shared;
      }
    };
  })
  .directive('two', function() {
    return {
      restrict: 'E',
      scope: {},
      template: '<p> {{ shared.val }}</p>',
      controller: function($scope, Shared) {
        $scope.shared = Shared;
      }
    };
  })
  .factory('Shared', function() {
    return {
      val: ''
    };
  });

scope.$parent.$apply()

app.directive('parent', function() {
    return {
        link: function(scope, elem, attrs) {
             scope.value = 'parent'            
        }
    }
});

app.directive('child', function() {
    return {
        scope: true,
        link: function(scope, elem, attrs) {

            scope.value = 'child'

            elem.click(function() {
                scope.$parent.value = 'modded!!' // -- previously 'parent' 
                scope.$parent.$apply();
            })
        }
    }
});