如何使用angularJS正确绑定指令和控制器之间的范围

见http://jsfiddle.net/ahonaker/ADukg/2046/ – 这是JS

var app = angular.module('myApp',[]);

//myApp.directive('myDirective',function() {});
//myApp.factory('myService',function() {});

function MyCtrl($scope) {
    $scope.itemselected = "None";
    $scope.organizations = {
        "_id": "SEC Power Generation","Entity": "OPUNITS","EntityIDAttribute": "OPUNIT_SEQ_ID","EntityID": 2,"descendants": ["Eastern Conf Business Unit","Western Conf Business Unit","Atlanta","Sewanee"],children: [{
            "_id": "Eastern Conf Business Unit","Entity": "","EntityIDAttribute": "","EntityID": null,"parent": "SEC Power Generation","descendants": ["Lexington","Columbia","Knoxville","Nashville"],children: [{
                "_id": "Lexington","EntityID": 10,"parent": "Eastern Conf Business Unit"
            },{
                "_id": "Columbia","EntityID": 12,{
                "_id": "Knoxville","EntityID": 14,{
                "_id": "Nashville","EntityID": 4,"parent": "Eastern Conf Business Unit"
            }]
        }]
    };

    $scope.itemSelect = function (ID) {
        $scope.itemselected = ID;
    }
}

app.directive('navtree',function () {
    return {
        template: '<ul><navtree-node ng-repeat="item in items" item="item" itemselected="itemselected"></navtree-node></ul>',restrict: 'E',replace: true,scope: {
            items: '='
        }
    };
});

app.directive('navtreeNode',function ($compile) {
    return {
        restrict: 'E',template: '<li><a ng-click="itemSelect(item._id)">{{item._id}} - {{itemselected}}</a></li>',scope: {
            item: "=",itemselected: '='
        },controller: 'MyCtrl',link: function (scope,elm,attrs) {
            if ((angular.isDefined(scope.item.children)) && (scope.item.children.length > 0)) {
                var children = $compile('<navtree items="item.children"></navtree>')(scope);
                elm.append(children);
            }
        }
    };
});

这里是HTML

<div ng-controller="MyCtrl">
    Selected: {{itemselected}}

    <navtree items="organizations.children"></navtree>
</div>

注意列表是从模型生成的。并且ng-click调用该函数来设置父范围属性(itemselected)，但更改仅在本地发生。当我点击一个项目时，预期的行为是“已选择：无”应该更改为“所选：xxx”，其中xxx是被点击的项目。

我没有适当地绑定父范围和指令之间的属性吗？如何将属性更改传递给父范围？

希望这很清楚。

提前感谢任何帮助。