如何理解Vue的v-model指令的使用方法

本文主要讲解v-model指令，主要包括HTML元素的v-model和组件上的v-model两种，用四个简单的案例介绍v-model的使用。

案例一：HTML元素的v-model -输入框(text)

<!DOCTYPE html>
  <html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>v-model指令</title>
    <script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
  </head>
  <body>
    <div id="app4">
      {{price}}<br>
      <input v-model="price"><!-- 下行注释的语法糖 -->
      <!-- <input :value="price" @input="price = $event.target.value"> -->
    </div>
    <script>
      new Vue({
        el: '#app4',
        data: {
          price: '20'
        }
      });
    </script>
  </body>
</html>

案例二： 定制组件的v-model - 输入框(text)

<!DOCTYPE html>
  <html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>v-model指令</title>
    <script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
  </head>
  <body>
    <div id="app3">
      {{price}}
      <my-input v-model="price"></my-input><!-- 下行注释的语法糖 -->
      <!-- <my-input :value="price" @input="val => {price = val}"></my-input> -->
    </div>
    <script>
      Vue.component('my-input', {
        template: '<div></span><input type="text" ref="input" :value="value" @input="doThis"/></div>',
        props: {
          value: String
        },
        methods: {
          doThis() {
            this.$emit('input', this.$refs.input.value);
          }
        }
      });
      new Vue({
        el: '#app3',
        data: {
          price: '10'
        }
      });
    </script>
  </body>
</html>

案例三： 定制组件的v-model - 复选框(checkbox) - 2.2.0 新增

 <!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8">
      <title>v-model指令</title>
      <script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
    </head>
    <body>
      <div id="app2">
        {{fruit}}<!-- 观测数据变化 -->
        <my-checkbox v-model="fruit.apple" value="apple"></my-checkbox><!-- 下行注释的语法糖 -->
        <!-- <my-checkbox :checked="fruit.apple" @change="val => {fruit.apple = val}" value="apple"></my-checkbox> -->

        <my-checkbox v-model="fruit.peach" value="peach"></my-checkbox><!-- 下行注释的语法糖 -->
        <!-- <my-checkbox :checked="fruit.peach" @change="val => {fruit.peach = val}" value="peach"></my-checkbox> -->
      </div>
      <script>
        Vue.component('my-checkbox', {
          template: '<div><span>{{value}}</span><input type="checkbox" :checked="checked" @change="doThis" :value="value"/></div>',
          model: {
            prop: 'checked',
            event: 'change'
          },
          props: {
            checked: Boolean,
            value: String
          },
          methods: {
            doThis() {
              this.$emit('change', !this.checked);
            }
          }
        });
        new Vue({
          el: '#app2',
          data: {
            fruit: {//数据
              apple: true,
              peach: false
            }
          }
        });
      </script>
    </body>
  </html>

案例四： 定制组件的v-model - 单选按钮(radio) -2.2.0 新增

<!DOCTYPE html>

<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>v-model指令</title>
  <script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
  <div id="app">
    {{fruit}}<!-- 观测数据变化 -->
    <my-radio v-model="fruit" value="apple" name="myFruit"></my-radio><!-- 下行注释的语法糖 -->
    <!-- <my-radio :checked="fruit" @change="val => {fruit = val}" value="apple"></my-radio> -->

    <my-radio v-model="fruit" value="peach" name="myFruit"></my-radio><!-- 下行注释的语法糖 -->
    <!-- <my-radio :checked="fruit" @change="val => {fruit = val}" value="peach"></my-radio> -->
  </div>
  <script>
    Vue.component('my-radio', {
      template: '<div><span>{{value}}</span><input :name="name" type="radio" ref="radio" :checked="checked===value" @change="doThis" :value="value"/></div>',
      model: {
        prop: 'checked',
        event: 'change'
      },
      props: {
        checked: String,
        value: String,
        name: String
      },
      methods: {
        doThis() {
          this.$emit('change', this.$refs.radio.value);
        }
      }
    });
    new Vue({
      el: '#app',
      data: {
        fruit: 'peach'//数据
      }
    });
  </script>
</body>
</html>

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