Vue组件v-for告警解决与指令详解

<flexbox v-if="roleShow" style="padding:15px; box-sizing: border-box;"> 
  <flexbox-item v-for="role in roles " > 
    <x-button mini :type="role.type" style="padding: 0 14px" @click.native="btnClick(role.action)">{{role.value}}</x-button> 
  </flexbox-item> 
</flexbox> 
<flexbox v-if="roleShow" style="padding:15px; box-sizing: border-box;">
  <flexbox-item v-for="role in roles " >
    <x-button mini :type="role.type" style="padding: 0 14px" @click.native="btnClick(role.action)">{{role.value}}</x-button>
  </flexbox-item>
</flexbox>出现告警：component lists rendered with v-for should have explicit keys. See https://vuejs.org/guide/list.html#key for more info.

<flexbox v-if="roleShow" style="padding:15px; box-sizing: border-box;"> 
  <flexbox-item v-for="(role,index) in roles " :key="index" > 
    <x-button mini :type="role.type" style="padding: 0 14px" @click.native="btnClick(role.action)">{{role.value}}</x-button> 
  </flexbox-item> 
</flexbox> 

<!DOCTYPE html>
<html>
<head>
  <title></title>
  <meta charset="utf-8">
  <script src="http://unpkg.com/vue/dist/vue.js"></script>
  <script type="text/javascript">
    window.onload = function(){
      var vm = new Vue({
        el:'#box',
        data:{
          arr:['1','2','3'],
          json:{a:'a',b:'b'}
        }
      });
    }
  </script>
</head>
<body>
  <div id="box">
    <p>循环数组</p>
    <ul>
      <li v-for="a in arr">
      {{a}}
      </li>
    </ul>
    <hr>
    <p>循环出数组索引</p>
    <ul>
      <li v-for="(v,k) in arr">
      {{v}}==>{{k}}
　　　　　　　</li>
    </ul>
    <p>循环json</p>
    <ul>
      <li v-for="item in json">{{item}}</li>
    </ul>
    <p>循环json的键</p>
    <ul>
      <li v-for="(k,v) in json">
      {{k}}==>{{v}}
      </li>
    </ul>
  </div>
</body>
</html>