报错：[Vue warn]: Avoid mutating a

项目中遇到父组件传值 activeIndex

<Tabs :tabs="tabs" :activeIndex="activeIndex" ></Tabs>
<script >
export default{
 updated(){
          let currentRoute=this.$route.name;
           var arr=Array.from(this.$store.state.app.tabs);
           if(arr.indexOf(currentRoute)!=-1){

             this.activeIndex=this.$store.state.app.activeIndex=arr.indexOf(currentRoute).toString();
           }

        }
}
</script>

子组件接收该值

<template>
      <el-tabs type="card" v-model="activeIndex"    >
        <el-tab-pane v-for="(item,index) in tabs" :label="item"  :closable="index==0?false:true" :name="index.toString()"  ></el-tab-pane>
      </el-tabs>
</template>

<script>
  export default{
      data(){
            return {
              tabs:[],
          }
        },

      props:['activeIndex']

    }
</script>

6ebadbe553e2f174006b.jpg

参考网址https://juejin.im/entry/5843abb1a22b9d007a97854c
由于父组件updated()方法中更改了this.activeIndex值，update方法除了父组件触发这个方法，子组件也会触发，即子组件会更改activeIndex的值，但是由于父子组件的传递机制，会造成报错Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders....
因此在子组件使用该值时需要经过新变量（currentIndex）重新传递，这样当这个值变更时，不会造activeIndex的更改

//v-model绑定更改
<el-tabs type="card" v-model="currentIndex"  >   
</el-tabs>
<script>
  export default{
      data(){
            return {
              tabs:[],
              currentIndex:this.activeIndex //currentIndex接收父组件传来的activeIndex值；
          }
        },

      props:['activeIndex']

    }
</script>