1，shallowReactive 与 shallowRef
- shallowReactive : only handles the responsiveness of the outermost properties in the object (that is, the shallow responsiveness);
- shallowRef: only handles the response type of value, does not perform reactive processing of objects
<template>
<h2>App</h2>
<h3>m1: {
{m1}}</h3>
<h3>m2: {
{m2}}</h3>
<h3>m3: {
{m3}}</h3>
<h3>m4: {
{m4}}</h3>
<button @click="update">更新</button>
</template>
<script lang="ts">
import {
reactive, ref, shallowReactive, shallowRef } from 'vue'
/*
shallowReactive与shallowRef
shallowReactive: 只处理了对象内最外层属性的响应式(也就是浅响应式)
shallowRef: 只处理了value的响应式, 不进行对象的reactive处理
总结:
reactive与ref实现的是深度响应式, 而shallowReactive与shallowRef是浅响应式
什么时候用浅响应式呢?
一般情况下使用ref和reactive即可,
如果有一个对象数据, 结构比较深, 但变化时只是外层属性变化 ===> shallowReactive
如果有一个对象数据, 后面会产生新的对象来替换 ===> shallowRef
*/
export default {
setup () {
const m1 = reactive({
a: 1, b: {
c: 2}})
const m2 = shallowReactive({
a: 1, b: {
c: 2}})
const m3 = ref({
a: 1, b: {
c: 2}})
const m4 = shallowRef({
a: 1, b: {
c: 2}})
const update = () => {
// m1.b.c += 1
// m2.b.c += 1
// m3.value.a += 1
m4.value.a += 1
}
return {
m1,
m2,
m3,
m4,
update,
}
}
}
</script>
2，readonly 与 shallowReadonly
- readonly: deep read-only data, a read-only proxy that takes an object (reactive or plain) or ref and returns the original proxy, read-only proxies are deep: any nested properties accessed are also read-only.
- shallowReadonly: shallow read-only data, creates a proxy to make its own property read-only, but does not perform deep read-only conversion of nested objects.
- Application scenario: In some specific cases, we may not want to update the data, so we can wrap and generate a read-only proxy object to read the data, but cannot modify or delete it.
<template>
<h2>App</h2>
<h3>{
{state}}</h3>
<button @click="update">更新</button>
</template>
<script lang="ts">
import {
reactive, readonly, shallowReadonly } from 'vue'
/*
readonly: 深度只读数据
获取一个对象 (响应式或纯对象) 或 ref 并返回原始代理的只读代理。
只读代理是深层的：访问的任何嵌套 property 也是只读的。
shallowReadonly: 浅只读数据
创建一个代理，使其自身的 property 为只读，但不执行嵌套对象的深度只读转换
应用场景:
在某些特定情况下, 我们可能不希望对数据进行更新的操作, 那就可以包装生成一个只读代理对象来读取数据, 而不能修改或删除
*/
export default {
setup () {
const state = reactive({
a: 1,
b: {
c: 2
}
})
// const rState1 = readonly(state)
const rState2 = shallowReadonly(state)
const update = () => {
// rState1.a++ // error
// rState1.b.c++ // error
// rState2.a++ // error
rState2.b.c++
}
return {
state,
update
}
}
}
</script>
3. toRaw and markRaw
- toRaw: Turn the proxy object into an ordinary object, and the interface will not change when the data changes.
- markRaw: Marks an object so that it will never be converted to a proxy and is no longer reactive.
<template>
<h2>{
{state}}</h2>
<button @click="testToRaw">测试toRaw</button>
<button @click="testMarkRaw">测试markRaw</button>
</template>
<script lang="ts">
import {
markRaw, reactive, toRaw } from 'vue'
export default {
setup () {
const state = reactive<any>({
name: 'tom',
age: 25,
})
const testToRaw = () => {
const user = toRaw(state)
user.age++ // 界面不会更新
}
const testMarkRaw = () => {
const likes = ['a', 'b']
// state.likes = likes
state.likes = markRaw(likes) // likes数组就不再是响应式的了
setTimeout(() => {
state.likes[0] += '--'
}, 1000)
}
return {
state,
testToRaw,
testMarkRaw,
}
}
}
</script>
4，toRef
A property on the source responsive object creates a ref object, the two internally operate on the same data value, and the two are synchronized when updated.
Difference ref: Copy a new data value to operate independently, and do not affect each other when updating.
Application:: toRef is useful when you want to pass the ref of a prop to a composite function
<template>
<h2>App</h2>
<p>{
{state}}</p>
<p>{
{foo}}</p>
<p>{
{foo2}}</p>
<button @click="update">更新</button>
<Child :foo="foo"/>
</template>
<script lang="ts">
/*
toRef:
为源响应式对象上的某个属性创建一个 ref对象, 二者内部操作的是同一个数据值, 更新时二者是同步的
区别ref: 拷贝了一份新的数据值单独操作, 更新时相互不影响
应用: 当要将某个 prop 的 ref 传递给复合函数时，toRef 很有用
*/
import {
reactive, toRef, ref } from 'vue'
import Child from './Child.vue'
export default {
setup () {
const state = reactive({
foo: 1,
bar: 2
})
const foo = toRef(state, 'foo')
const foo2 = ref(state.foo)
const update = () => {
state.foo++
// foo.value++
// foo2.value++ // foo和state中的数据不会更新
}
return {
state,
foo,
foo2,
update,
}
},
components: {
Child
}
}
</script>
5. The principle of customRef -------- ref
Create a custom ref and explicitly control its dependency tracking and update triggering;
there are two callback functions, one is track() to tell Vue to monitor and track data, and the other is trigger() to trigger updates;
<template>
<h2>App</h2>
<input v-model="keyword" placeholder="搜索关键字"/>
<p>{
{keyword}}</p>
</template>
<script lang="ts">
/*
customRef:
创建一个自定义的 ref，并对其依赖项跟踪和更新触发进行显式控制
需求:
使用 customRef 实现 debounce 的示例
*/
import {
ref,
customRef
} from 'vue'
export default {
setup () {
const keyword = useDebouncedRef('', 500)
console.log(keyword)
return {
keyword
}
},
}
/*
实现函数防抖的自定义ref
*/
function useDebouncedRef<T>(value: T, delay = 200) {
let timeout: number
return customRef((track, trigger) => {
return {
get() {
// 告诉Vue追踪数据
track()
return value
},
set(newValue: T) {
clearTimeout(timeout)
timeout = setTimeout(() => {
value = newValue
// 告诉Vue去触发界面更新
trigger()
}, delay)
}
}
})
}
</script>
6. Provide and inject implement component communication
- Provide and inject provide dependency injection, which is similar to Vue2's provide/inject ;
- Realize communication between cross-level components (grandfather and grandchildren, cross-domain parent-child component communication and direct grandparent communication);
<template>
<h1>父组件</h1>
<p>当前颜色: {
{color}}</p>
<button @click="color='red'">红</button>
<button @click="color='yellow'">黄</button>
<button @click="color='blue'">蓝</button>
<hr>
<Son />
</template>
<script lang="ts">
import {
provide, ref } from 'vue'
/*
- provide` 和 `inject` 提供依赖注入，功能类似 2.x 的 `provide/inject
- 实现跨层级组件(祖孙)间通信
*/
import Son from './Son.vue'
export default {
name: 'ProvideInject',
components: {
Son
},
setup() {
const color = ref('red')
provide('color', color)
return {
color
}
}
}
</script>
<template>
<div>
<h2>子组件</h2>
<hr>
<GrandSon />
</div>
</template>
<script lang="ts">
import GrandSon from './GrandSon.vue'
export default {
components: {
GrandSon
},
}
</script>
<template>
<h3 :style="{color}">孙子组件: {
{color}}</h3>
</template>
<script lang="ts">
import {
inject } from 'vue'
export default {
setup() {
const color = inject('color')
return {
color
}
}
}
</script>
7. Judgment of responsive data
- isRef: checks if a value is a ref object;
- isReactive: checks if an object is a reactive proxy created by reactive;
- isReadonly: checks whether an object is a read-only proxy created by readonly;
- isProxy: checks whether an object is a proxy created by a reactive or readonly method;