基于vue.js中关于下拉框的值默认及绑定问题

<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>