AngularJS中的下拉列表具有正确的文本，但值不正确

Here's my dropdown:

这是我的下拉菜单:

<select class="form-control form-controls input-sm" ng-model="vm.retailer.state" ng-options="state.code as state.name for state in vm.states" required>
    <option value="">-- Select a State --</option>
</select>
<select class