自定义指令模型在ng-switch中不起作用

Question

我正在尝试使用AngularJS来提供一个可切换的下拉列表,其中各种选项的选择将触发不同的列表.ng-switch看起来是正确的方式,但我的内心ng-model并没有约束力ng-switch.如果我不使用绑定工作正常ng-switch,但如果是这种情况我不知道如何切换我的下拉列表.这可能是什么问题？

jsFiddle:http://jsfiddle.net/tanweihao88/LUzXT/3/

HTML:

<select ng-model="periodRangeModel" ng-options="item for item in items"></select>
<div ng-switch on="periodRangeModel">
    <span ng-switch-when="Month"><period-selector items="monthOptions" ng-model="periodModel"></period-selector></span>
    <span ng-switch-when="Quarter"><period-selector items="quarterOptions" ng-model="periodModel"></period-selector></span>
    <br>
</div>

JS:

angular.module('myApp', [])
.controller("MyCtrl", function($scope) {
    $scope.items = ['Month', 'Quarter'];
    $scope.periodRangeModel = "Month";
    $scope.quarterOptions = ["Jan-Mar", "Apr-Jun", "Jul-Sept", "Oct-Dec"];
    $scope.monthOptions = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
    $scope.periodModel = $scope.monthOptions[0];
})
.directive('periodSelector', function() {
    return {
        restrict: 'E',
        replace: true,
        scope: { items: '=', ngModel: '='},
        template: "<span><select ng-options='period for period in items' ng-model='ngModel'></select></span>"
    }
});

Answer 1

绑定不能按预期工作的主要原因是ng-switch创建一个新范围,当绑定到字符串原语时,原始文件periodModel未按预期更新(因为新范围periodModel正在更新).

这个问题详细介绍了幕后发生的事情,你可以查看Angular Batarang Chrome Extension,直观地看到各种范围.

你可以通过绑定到像这个更新的小提琴中的对象值来解决它.主要变化是:

1)更改periodModel为对象并设置属性(在此示例中称为value)

$scope.periodModel = {
    value: $scope.monthOptions[0]
};

2)更改任何绑定代码periodModel.value而不是periodModel

<period-selector items="monthOptions" ng-model="periodModel.value"></period-selector>

Model: {{periodModel.value}} (this is supposed to change)