vue3的新写法和特性整理——五、子组件向组件向父组件暴露方法

vue3中子组件向父组件暴露方法并传值，同样兼容老写法
1、父组件

<template>
  <div class="home">
    <h1>父组件</h1>
    <img alt="Vue logo" src="../assets/logo.png" />
    <HelloWorld @changeMsg="changeMsg" :msg="msg" />
    <h1>{{num}}</h1>
  </div>
</template>
 
<script>
import { reactive, toRefs } from 'vue';
import HelloWorld from '@/components/HelloWorld';
export default {
  setup() {
    const state = reactive({
      msg: '点击修改父组件传值',
      num: 0
    });
    let changeMsg = x => {
      state.num += x;
    };
 
    return {
      ...toRefs(state),
      changeMsg
    };
  },
  name: 'Home',
  components: { HelloWorld }
};
</script>
 
<style scoped>
.home {
  color: red;
  border: 1px solid red;
   
}
</style>

2、子组件

<template>
  <div class="hello">
    <h1>子组件</h1>
    <h1 class="pointer" @click="notifyParent">{{ msg }}</h1>
  </div>
</template>
 
<script>
import { toRefs } from 'vue';
export default {
  setup(props, context) {
    console.log(context);
 
    let notifyParent = () => {
      context.emit('change-msg', 2);
    };
    return {
      ...toRefs(props),
      notifyParent
    };
  },
  name: 'HelloWorld',
  props: {
    msg: String
  }
};
</script>
 
<style scoped>
.hello {
  margin: 20px;
  color: green;
  border: 1px solid green;
}
.pointer{
  cursor: pointer;
}
</style>