vue3的双向绑定 v-model实现原理和案例

parent.vue

<template>
    <span>v-model 默认传值span>
    <childVue v-model="value">
        <template #prefix>
            <span>子组件值：span>
        template>
        <template #suffix>
            <span>结果值：{{value}}span>
        template>
    childVue>

    <br><br>
    <span>单个组件中，绑定多个输入值span>
    <a-input type="text" v-model:value="value2" />
    <a-input type="text" v-model:value="value3" />
    <childVue2 v-model:Arg1="value2" v-model:Arg2="value3" v-model:Result="value4" />
    <span>结果值：{{ value4 }}span>

    <br><br>
    <span>带修饰符的 v-modelspan>
    <child3Vue v-model:title="value5" />
    <span>不传修饰符: {{ value5 }}span>
    <br><br>
    <child3Vue v-model:title.smile="value6" />
    <span>传入修饰符 smile: {{ value6 }}span>
    <br><br>
    <child3Vue v-model:title.cry="value7" />
    <span>传入修饰符 cry: {{ value7 }}span>
    <br><br>
template>
<script setup>
import { ref } from 'vue';
import childVue from './child.vue';
import childVue2 from './child2.vue';
import child3Vue from './child3.vue';
// 默认传值
const value = ref();

// 传多个参数进行绑定;
const value2 = ref();
const value3 = ref();
const value4 = ref();

// 带修饰符的参数绑定
const value5 = ref();
const value6 = ref();
const value7 = ref();
script>
<style lang="less" scoped>

style>
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child.vue

<template>
    <a-input type="text" v-model:value="inputModelValue">
        <template #prefix>
            <slot name="prefix">slot>
        template>
        <template #suffix>
            <slot name="suffix">slot>
        template>
    a-input>
template>
<script setup>
import { ref, watch } from 'vue';

// 默认值显示用参数
const inputModelValue = ref();

const props = defineProps({
    // 默认参数值 注意传参的默认值为 modelValue
    modelValue: [Number, String],
});

const emit = defineEmits([
    // 为更新事件命名
    'update:modelValue'
]);

// 父级改变时，修改本组件中变量的值
watch(() => props.modelValue, val => {
    inputModelValue.value = val;
    // 加上这个参数，在初始化的时候进行一次传参相应
}, { immediate: true });

// 本组件中变量改变时，通知父级组件进行更新
watch(inputModelValue, (val) => {
    emit('update:modelValue', val);
})


script>
<style lang="less" scoped>

style>
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child2.vue

<template>template>

<script setup>
import { ref, watch } from 'vue';
const props = defineProps({
    Arg1: [Number, String],
    Arg2: [Number, String],
    Result: [Number, String],
});

const emit = defineEmits(['update:Result'])

watch(() => [props.Arg1, props.Arg2], (newValue, oldValue) => {
    // Wacth 监听多个数据的返回值时, 是按照数组下标进行传递的
    emit('update:Result', (newValue[0] || '') + ' ' + (newValue[1] || ''));
})


script>
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child3.vue

<template>
    <a-input v-model:value="value" />
template>
<script setup>
import { ref, watch } from 'vue';
const props = defineProps({
    'title': {
        default: ''
    },
    // 对于又有参数又有修饰符的 v-model 绑定，生成的 prop 名将是 arg + "Modifiers"
    'titleModifiers': {
        default: () => { return {} }
    }
});

const emit = defineEmits([
    // 为更新事件命名
    'update:title'
]);
const value = ref('');

value.value = props.title;
watch(value, val => {
    if (props.titleModifiers.smile) {
        emit('update:title', val + '😀');
    } else if (props.titleModifiers.cry) {
        emit('update:title', val + '😂');
    } else {
        emit('update:title', val);
    };
}, { immediate: true });


script>
<style lang="less" scoped>

style>
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