如何通过ng-bind绑定变量

html代码：

<div ng-app="MyApp">
    <div ng-controller="MyController">
        <div>
            <div ng-bind="cdkey.name">
            初始值
        </div>
        <div>{{cdkey.name}}</div>
        <input type="text" ng-model="cdkey.name">
            {{cdkey.name}}
        </div>
            <hr>
            <div>
            <div ng-bind="cdkey.key">
            初始值
        </div>
        <div>{{cdkey.key}}</div>
        <input type="text" ng-model="cdkey.key">
            {{cdkey.key}}
        </div>
    </div>
</div>

js代码

angular.module("MyApp", [])
.controller("MyController", ["$scope", function($scope){
    $scope.cdkey = {
        name: {
            hello: "Hello, World"
        },
        key: "hello"
    }
}])