AngularJs ng-model绑定问题

<h2>一、单选radioh2>
<h3>1.1 最简单radioh3>
<div>
    <input type="radio" value="1" ng-model="selectValue"/>语文
    <input type="radio" value="2" ng-model="selectValue"/>数学
    <input type="radio" value="3" ng-model="selectValue"/>英语
div>
<div>selectValue:{{selectValue}}div>
<h3>1.2 因为ng-repeat的子scope无法关联ng-model的radioh3>
<div>
    <label ng-repeat="rd in subjectlist">
        <input type="radio" ng-model="radioModelOfSubScope" value="{{rd.subjectCode}}" name="subjectRadio">{{rd.subjectName}}
    label>
div>
<span>无法得到此处"{{radioModelOfSubScope}}"的值,因为ng-repeat之间的东西都归属于子scope管理，不再属于全局$scopespan>
<div>radioModelOfSubScope:{{radioModelOfSubScope}}div>
<h3>1.3 利用$parent关联ng-model的radioh3>
<div>
    <label ng-repeat="rd in subjectlist">
        
        <input type="radio" ng-model="$parent.radioModelOfGlobelScope" value="{{rd.subjectCode}}"  name="subjectRadio">{{rd.subjectName}}
        
    label>
div>
<div>radioModelOfGlobelScope:{{radioModelOfGlobelScope}}div>

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页面效果如下：