子组件：
<template>

  <div class="hello">

    <button v-on:click="onClickMe">telltofather</button>

  </div>

</template>

<script>

export default {

  methods: {

    onClickMe () {

      this.$emit('childClick',this.msg);//将this.msg传给父组件

    }

  }

}

</script>

<template>

    <div id="app">

    <p>child tell me: {{childWords}}</p>

    <child v-on:childClick='listenToMyBoy'>

    </child>

</div>

</template   >

<script>

import child from './components/child';

export default {

  components: {

    child

  },

  data () {

    return {

      childWords: ''

    }

  },

  methods: {

    listenToMyBoy (msg) {

      this.childWords = msg;//获取到子组件传过来的值msg

    }

  }

}

</script>