8.生命周期

vue2.x的生命周期

vue3.0的生命周期

Vue3.0中可以继续使用Vue2.x中的生命周期钩子，但有有两个被更名：
- beforeDestroy改名为 beforeUnmount
- destroyed改名为 unmounted
Vue3.0也提供了 Composition API 形式的生命周期钩子，与Vue2.x中钩子对应关系如下：
- beforeCreate===>setup()
- created=======>setup()
- beforeMount ===>onBeforeMount
- mounted=======>onMounted
- beforeUpdate===>onBeforeUpdate
- updated =======>onUpdated
- beforeUnmount ==>onBeforeUnmount
- unmounted =====>onUnmounted

components

Demo.vue

<template>
	<h2>当前求和为：{{sum}}</h2>
	<button @click="sum++">点我+1</button>
</template>

<script>
	import {ref,onBeforeMount,onMounted,onBeforeUpdate,onUpdated,onBeforeUnmount,onUnmounted} from 'vue'
	export default {
		name: 'Demo',
		
		setup(){
			console.log('---setup---')
			//数据
			let sum = ref(0)

			//通过组合式API的形式去使用生命周期钩子
			onBeforeMount(()=>{
				console.log('---onBeforeMount---')
			})
			onMounted(()=>{
				console.log('---onMounted---')
			})
			onBeforeUpdate(()=>{
				console.log('---onBeforeUpdate---')
			})
			onUpdated(()=>{
				console.log('---onUpdated---')
			})
			onBeforeUnmount(()=>{
				console.log('---onBeforeUnmount---')
			})
			onUnmounted(()=>{
				console.log('---onUnmounted---')
			})

			//返回一个对象（常用）
			return {sum}
		},
		//通过配置项的形式使用生命周期钩子
		//#region 
		beforeCreate() {
			console.log('---beforeCreate---')
		},
		created() {
			console.log('---created---')
		},
		beforeMount() {
			console.log('---beforeMount---')
		},
		mounted() {
			console.log('---mounted---')
		},
		beforeUpdate(){
			console.log('---beforeUpdate---')
		},
		updated() {
			console.log('---updated---')
		},
		beforeUnmount() {
			console.log('---beforeUnmount---')
		},
		unmounted() {
			console.log('---unmounted---')
		},
		//#endregion
	}
</script>

App.vue

<template>
	<button @click="isShowDemo = !isShowDemo">切换隐藏/显示</button>
	<Demo v-if="isShowDemo"/>
</template>

<script>
	import {ref} from 'vue'
	import Demo from './components/Demo'
	export default {
		name: 'App',
		components:{Demo},
		setup() {
			let isShowDemo = ref(true)
			return {isShowDemo}
		}
	}
</script>

main.js

//引入的不再是Vue构造函数了，引入的是一个名为createApp的工厂函数
import { createApp } from 'vue'
import App from './App.vue'

//创建应用实例对象——app(类似于之前Vue2中的vm，但app比vm更“轻”)
const app = createApp(App)

//挂载
app.mount('#app')