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父组件传入子组个的变量， 子组件是无法直接修改的， 只能通过 emit的方式， 让父组件修改， 之后子组件更新

<template><div class="parent">我是父组件<son :msg="msg" :obj="obj" @changemsgEmit="changemsgEmit" @changeobjnameEmit="changeobjnameEmit" @changeobjageEmit="changeobjageEmit"></son></div>
</template><script setup>import {ref, reactive} from "vue";import son from "./son.vue"let msg = ref("this msg form parent.vue");let obj = reactive({name:"huang",age:39})const changeobjageEmit = (params)=>{obj.age = params;}const changeobjnameEmit = (params)=>{obj.name = params.newname;}const changemsgEmit = (params)=>{console.log(params);msg.value = params.join("");}</script><style scoped></style>

父组件的写法没有变， 子组件的写法就有很大的变化了

<template><div class="son">son{{msg}}<hr/>{{obj.name}}{{obj.age}}</div><button @click="changemsg">changemsg</button><button @click="changeobjname(3)" type="button">changeobjname</button><button @click="changeobjage(42)" type="button">changeobjage</button>
</template><script setup>
//这里定义了一个 props来接收传来的属性
//使用时可以是 {{msg}}  也可以使用 {{props.msg}}let props = defineProps({msg:{type:String,default:""},obj:{type:Object,default:{}}})//这里定义了三个自定义事件const emit = defineEmits(["changeobjnameEmit","changeobjageEmit","changemsgEmit"]);//下面是通过事件调用了三个自定义的事件const changeobjname = ()=>{let objname = {newname:"hahaha"}emit("changeobjnameEmit",objname)}const changeobjage = (age)=>{emit("changeobjageEmit",age)}const changemsg = ()=>{emit("changemsgEmit",["aa","bb","cc"]);}</script>