1、v-model
Vue2
Vue2中得 v-model 默认解析成 :value 与 @input
原理实现
父:
html
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld :value="count" @input="count = $event"></HelloWorld>
</div>
</template>
<script>
import HelloWorld from "./components/HelloWorld.vue";
export default {
name: "App",
components: {
HelloWorld,
},
data() {
return { count: 0 };
}
};
</script>
<style></style>子:
html
<template>
<div>
{{ value }}
<button @click="$emit('input', value + 1)">+1</button>
</div>
</template>
<script>
export default {
name: "HelloWorld",
props: {
value: Number,
},
};
</script>
<style scoped></style>语法糖实现
父:
html
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld v-model="count" />
</div>
</template>
<script>
import HelloWorld from "./components/HelloWorld.vue";
export default {
name: "App",
components: {
HelloWorld,
},
data() {
return { count: 0 };
}
};
</script>
<style></style>子:
html
<template>
<div>
{{ value }}
<button @click="$emit('input', value + 1)">+1</button>
</div>
</template>
<script>
export default {
name: "HelloWorld",
props: {
value: Number,
},
};
</script>
<style scoped></style>Vue3
Vue3中得 v-model 默认解析成 :modelValue 与 @update:modelValue
原理实现
父:
html
<script setup lang="ts">
import { ref } from 'vue'
const count = ref(0)
</script>
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld
:modelValue="count"
@update:modelValue="count = $event"
></HelloWorld>
</div>
</template>
<style lang="scss" scoped></style>子:
html
<script setup lang="ts">
defineProps<{
modelValue: number
}>()
defineEmits<{
(e: 'update:modelValue', newCount: number): void
}>()
</script>
<template>
<div>
{{ modelValue }}
<button @click="$emit('update:modelValue', modelValue + 1)">+1</button>
</div>
</template>
<style lang="scss" scoped></style>语法糖实现
父：
html
<script setup lang="ts">
import { ref } from 'vue'
const count = ref(0)
</script>
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld v-model="count"></HelloWorld>
</div>
</template>
<style lang="scss" scoped></style>子:
html
<script setup lang="ts">
defineProps<{
modelValue: number
}>()
defineEmits<{
(e: 'update:modelValue', newCount: number): void
}>()
</script>
<template>
<div>
{{ modelValue }}
<button @click="$emit('update:modelValue', modelValue + 1)">+1</button>
</div>
</template>
<style lang="scss" scoped></style>2、 .sync
Vue2
Vue2中得 :attr.sync 默认解析成 :attr 与 @update:attr
原理实现
父：
html
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld :count="count" @setCount="count = $event" />
</div>
</template>
<script>
import HelloWorld from "./components/HelloWorld.vue";
export default {
name: "App",
components: {
HelloWorld,
},
data() {
return { count: 0 };
}
};
</script>
<style></style>子：
html
<template>
<div class="hello">
{{ count }}
<button @click="$emit('setCount', count + 1)">+1</button>
</div>
</template>
<script>
export default {
name: "HelloWorld",
props: {
count: Number,
},
};
</script>
<style scoped></style>语法糖实现
父：
html
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld :count.sync="count" />
</div>
</template>
<script>
import HelloWorld from "./components/HelloWorld.vue";
export default {
name: "App",
components: {
HelloWorld,
},
data() {
return { count: 0 };
}
};
</script>
<style></style>子：
html
<template>
<div class="hello">
{{ count }}
<button @click="$emit('update:count', count + 1)">+1</button>
</div>
</template>
<script>
export default {
name: "HelloWorld",
props: {
count: Number,
},
};
</script>
<style scoped></style>Vue3
Vue3中得 v-model:attr 默认解析成 :attr 与 @update:attr
原理实现
父:
html
<script setup lang="ts">
import { ref } from 'vue'
const count = ref(0)
</script>
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld :count="count" @setCount="count = $event"></HelloWorld>
</div>
</template>
<style lang="scss" scoped></style>子:
html
<script setup lang="ts">
defineProps<{
count: number
}>()
defineEmits<{
(e: 'setCount', newCount: number): void
}>()
</script>
<template>
<div>
{{ count }}
<button @click="$emit('setCount', count + 1)">+1</button>
</div>
</template>
<style lang="scss" scoped></style>语法糖实现
父:
html
<script setup lang="ts">
import { ref } from 'vue'
const count = ref(0)
</script>
<template>
<div>
{{ count }}
<button @click="count++">+1</button>
<hr />
<HelloWorld v-model:count="count"></HelloWorld>
</div>
</template>
<style lang="scss" scoped></style>子:
html
<script setup lang="ts">
defineProps<{
count: number
}>()
defineEmits<{
(e: 'update:count', newCount: number): void
}>()
</script>
<template>
<div>
{{ count }}
<button @click="$emit('update:count', count + 1)">+1</button>
</div>
</template>
<style lang="scss" scoped></style>3、总结
Vue2中得 v-model 默认解析成 :value 与 @input
Vue3中得 v-model 默认解析成 :modelValue 与 @update:modelValue
Vue2中得 :attr.sync 默认解析成 :attr 与 @update:attr
Vue3中得 v-model:attr 默认解析成 :attr 与 @update:attr
作用：用于在自定义组件中实现父子组件之间的双向数据绑定
也就是说在Vue3中只有v-model,没有.sync
如果父组件只写v-model="xxx",子组件中接收到的props为modelValue ,抛出的自定义事件为update:modelValue
如果父组件写v-model:attr="xxx" (attr为自定义变量),子组件中接收到的props为attr ,抛出的自定义事件为update:attr
即：Vue3中使用双向数据绑定v-model时props不局限于只能接收modelValue,可以自定义
使用方式：
ts
父：
<HelloWorld v-model="count"></HelloWorld>
子：
defineProps<{
modelValue: number
}>()
defineEmits<{
(e: 'update:modelValue', newCount: number): void
}>()
$emit('update:modelValue', modelValue + 1)"
=====================================================================================
父：
<HelloWorld v-model:count="count"></HelloWorld>
子：
defineProps<{
count: number
}>()
defineEmits<{
(e: 'update:count', newCount: number): void
}>()
$emit('update:count', count + 1)">