Vue父组件如何获取子组件中的变量

<template>
 <div class="DbSource-box">
 <el-button type="primary" icon="" class="addBtn" @click="addDbSource()">新增</el-button>
 <db-source-add ref="addAlert" v-on:init="init"></db-source-add>
 </div>
</template>
 
<script>
 import DbSourceAdd from "../components/DbSourceManager/DbSourceAdd";
 export default {
 name: "DbSourceManager",
 components: {DbSourceAdd},
 methods: {
  // 点击新增按钮，弹出新增数据源的弹框
  addDbSource(){
  this.$refs.addAlert.$el.style.display = "block";
  },
 }
 }
</script>

<template>
 <div class="DbSource-box">
 <el-button type="primary" icon="" class="selectBtn" @click="deleteSelectDbSource()">批量删除</el-button>
 <db-source-table ref="getSelectData" :Data="Data" v-on:init="init"></db-source-table>
 </div>
</template>
 
<script>
 import DbSourceTable from "../components/DbSourceManager/DbSourceTable";
 export default {
 name: "DbSourceManager",
 components: {DbSourceTable},
 methods: {
  // 删除选中的数据源（批量删除）
  deleteSelectDbSource(){
  console.log(this.$refs.getSelectData.multipleSelection)
  },
 }
 }
</script>

<template>
 <div class="table-box">
 
 </div>
</template>
 
<script>
 export default {
 name: "DbSourceTable",
 props:["Data"],
 data(){
  return {
  multipleSelection:[],
  pagesize: 3,
  currpage: 1,
  currId:""
  }
 }
</script>