AngularJS Material 下拉选项不起作用

AngularJS Material dropdown options not working

我正在尝试使用 AngularJS Material 构建表单,但在显示下拉选项时遇到问题。我的 HTML 在下面,我的选项存储在服务器脚本的对象数组中。我在下面做错了什么?

<md-input-container class="md-block" flex-gt-sm ng-switch-when="choice">
    <label for="{{element.section_element_name}}">{{element.section_element_label}}</label>
    <md-select id={ {element.section_element_name}} type="selectbasic" value={{element.q_value}}>
        <md-option ng-repeat="option in element.section_element_choices" value="{{option.element_choice_value}}">
            {{option.element_choice_label}}
        </md-option>
    </md-select>
</md-input-container>
<md-input-container class="md-block" flex-gt-sm ng-switch-when="choice">
  <label for="{{element.section_element_name}}">{{element.section_element_label}}</label>
  <md-select id={ {element.section_element_name}} type="selectbasic" ng-model="selectedItem">
    <md-option ng-repeat="option in element.section_element_choices" value="{{option.element_choice_value}}">
        {{option.element_choice_label}}
    </md-option>
</md-select>