javascript - Angular : Select doesn't change selected option on change of bound scope variable

Question

我有一个选择控件。它的选项是从作用域的对象数组动态生成的。在应用程序初始化时，我想通过更改作用域上的绑定(bind)变量来选择特定选项。

当 select 的 ng-option 返回完整对象时，它不起作用。但是，它在 select 的 ng-option 返回字符串时有效。

是 Angular 错误还是我做错了什么？

HTML:

<div ng-controller="selectCtrl" ng-app>
    Doesn't work when select's ngModel value is object:<br />
    <select ng-model="valueObject" ng-options="o.label for o in options"></select><br />
    <pre>{{valueObject | json}}</pre>

    Works when select's ngModel value is string:<br />
    <select ng-model="valueString" ng-options="o.value as o.label for o in options"></select>
    <pre>{{valueString | json}}</pre>    

JS:

function selectCtrl($scope) {    
   $scope.options = [
       {label: 'a', value: '1', someId: 333},
       {label: 'b', value: '2', someId: 555}
   ];    
   $scope.valueObject = {label: 'a', value: '1', someId: 333};
   $scope.valueString = '1';
};

JS fiddle :http://jsfiddle.net/apuchkov/FvsKW/6/

Answer 1

"Track by"expression 必须用于在我的问题中制作示例。更多详情:http://leoshmu.wordpress.com/2013/09/11/making-the-most-of-ng-select/

更新的 JsFiddle:http://jsfiddle.net/apuchkov/FvsKW/9/

HTML

<div ng-controller="selectCtrl" ng-app>
    Doesn't work when select's ngModel value is object:<br />
    <select ng-model="valueObject" ng-options="o.label for o in options"></select><br />
    <pre>{{valueObject | json}}</pre>

    Does work when select's ngModel value is object AND 'track by' expression is used:<br />
    <select ng-model="valueObject" ng-options="o.label for o in options track by o.value"></select><br />
    <pre>{{valueObject | json}}</pre>
</div>

JS

function selectCtrl($scope) {    
    $scope.options = [
        {label: 'a', value: '1', someId: 333},
        {label: 'b', value: '2', someId: 555}
    ];    
    $scope.valueObject = {label: 'a', value: '1', someId: 333};
};