vue.js中关于下拉框的值默认及绑定问题

一、今天遇到vue中下拉框问题，故而写点东西留个脚印

<template>

  <select v-model='selected' @click="disable()">
    <option v-for="(option,index) in options" v-bind:value="option.value" :disabled="option.disabled">
      {{ option.text }}{{index}}{{option.disabled}}
    </option>
  </select>
  <span>Selected: {{ selected }}</span>
</template>
<script>
  export default{
    name: 'second',
    data(){
      return {
        selected: 'sex',   // 这里选择默认项
        options: [
          {text: '点击选择性别', value: 'sex', disabled: ''},
          {text: '男', value: '1'},
          {text: '女', value: '2'}
        ]
      }
    },
    methods: {
      disable: function () {
        this.options[0].disabled = disabled;
      },
    }
  }
</script>