<template>
   <div>
       <up :myMessage="value"  @update:myMessage="func"/>
   </div>
</template>

<script>
import up from './update'
export default {
   components: {
       up
   },
   data() {
       return {
           value: ''
       }
   },
   methods: {
       func(e){
           this.value = '父组件点击子组件并修改了子组件里面的值';
       }
   }
}
</script>

<template>
<div>
   <button @click="func">点击我改变</button>
   <p>{{myMessage}}</p>
</div>
</template>

<script>
export default {
   name: "update",
   props: ['myMessage'],
   methods: {
       func(params) {
           this.$emit('update:myMessage',params);
       }
   }
}
</script>