$emit

vm.$emit( event, […args] )

触发当前实例上的事件。附加参数都会传给监听器回调。

//父组件
<template>
    <ratingselect @select-type="onSelectType"></ratingselect>
</template>
<script>
    data () {
      return {
        selectType: 0,
    },
    methods: {
      onSelectType (type) {
        this.selectType = type
      }
    }
</script>

父组件使用@select-type="onSelectType"监听由子组件vm.$emit触发的事件，通过onSelectType()接受从子组件传递过来的数据，通知父组件数据改变了。

// 子组件
<template>
  <div>
    <span @click="select(0, $event)"  :class="{'active': selectType===0}"></span>
    <span @click="select(1, $event)"  :class="{'active': selectType===1}"></span>
    <span @click="select(2, $event)"  :class="{'active': selectType===2}"></span>
  </div>
</template>
<script>
    data () {
      return {
        selectType: 0,
    },
    methods: {
        select (type, event) {
            this.selectType = type
            this.$emit('select-type', type)
      }
    }
</script>