vue中在父组件点击按钮触发子组件的事件

<template>
  <div id="app">
    <!--父组件-->
    <input v-model="msg" />
    <button v-on:click="notify">广播事件</button>
    <!--子组件-->
    <popup ref="child"></popup>
  </div>
</template>
 <script>
import popup from "@/components/popup";
export default {
  name: "app",
  data: function () {
    return {
      msg: "",
    };
  },
  components: {
    popup,
  },
  methods: {
    notify: function () {
      if (this.msg.trim()) {
        this.$refs.child.parentMsg(this.msg);
      }
    },
  },
};
</script>
 <style>
#app {
  font-family: "Avenir", Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}
</style>

<template>
  <div>
    <ul>
      <li v-for="item in messages">父组件输入了：{{ item }}</li>
    </ul>
  </div>
</template>
  <style>
body {
  background-color: #ffffff;
}
</style>
  <script>
export default {
  name: "popup",
  data: function () {
    return {
      messages: [],
    };
  },
  methods: {
    parentMsg: function (msg) {
      this.messages.push(msg);
    },
  },
};
</script>