vue 子组件向父组件传值方法

<ponent-a v-on:child-say="listenToMyBoy"></ponent-a>
<p>Do you like me? {{childWords}}</p>
 methods: {
   listenToMyBoy: function (somedata){
    this.childWords = somedata
   }
  }

<button v-on:click="onClickMe">like!</button>
methods: {
  onClickMe: function(){
  this.$emit('child-say',this.somedata);
  }
 }