数量选择组件-基本结构

（1）准备基本结构

<script lang="ts" setup name="Numbox">
//
</script>
<template>
  <div class="numbox">
    <div class="label">数量</div>
    <div class="numbox">
      <a href="javascript:;">-</a>
      <input type="text" readonly value="1" />
      <a href="javascript:;">+</a>
    </div>
  </div>
</template>

<style scoped lang="less">
.numbox {
  display: flex;
  align-items: center;
  .label {
    width: 60px;
    color: #999;
    padding-left: 10px;
  }
  .numbox {
    width: 120px;
    height: 30px;
    border: 1px solid #e4e4e4;
    display: flex;
    > a {
      width: 29px;
      line-height: 28px;
      text-align: center;
      background: #f8f8f8;
      font-size: 16px;
      color: #666;
      &:first-of-type {
        border-right: 1px solid #e4e4e4;
      }
      &:last-of-type {
        border-left: 1px solid #e4e4e4;
      }
    }
    > input {
      width: 60px;
      padding: 0 5px;
      text-align: center;
      color: #666;
    }
  }
}
</style>

（2）全局注册

import Numbox from '@/components/numbox/index.vue'
export default {
  install(app: App) {
    app.component('Numbox', Numbox)
  },
}

（3）提供类型声明

import Numbox from '@/components/numbox/index.vue'
declare module 'vue' {
  export interface GlobalComponents {
    Numbox: typeof Numbox
  }
}

export {}

（4）渲染

<div class="spec">
  <!-- 数字选择框 -->
  <XtxNumbox></XtxNumbox>
</div>

效果

数量选择组件-v-model语法糖

目标：掌握vue3.0的v-model语法糖原理

在vue2.0中v-mode语法糖简写的代码 <Son :value="msg" @input="msg=$event" />

在vue3.0中v-model语法糖有所调整：<Son :modelValue="msg" @update:modelValue="msg=$event" />

演示代码：

<script lang="ts" setup>
defineProps({
  money: {
    type: Number,
    default: 0,
  },
})

const emit = defineEmits(['update:money'])
</script>

<template>
  <h3>子组件-{{ money }}</h3>
  <button @click="emit('update:money', money + 1)">+1</button>
</template>

<style scoped lang="less"></style>

总结： vue3.0封装组件支持v-model的时候，父传子:modelValue 子传父 @update:modelValue

补充： vue2.0的 xxx.sync 语法糖解析 父传子 :xxx 子传父 @update:xxx 在vue3.0 使用 v-model:xxx 代替。

数量选择组件-功能实现

大致功能分析：

• 默认值为1
• 可限制最大最小值
• 点击-就是减1 点击+就是加1
• 需要完成v-model得实现
• 存在无label情况

<script lang="ts" setup name="Numbox">
const props = defineProps({
  modelValue: {
    type: Number,
    default: 1,
  },
  min: {
    type: Number,
    default: 1,
  },
  max: {
    type: Number,
    default: 20,
  },
  showLabel: {
    type: Boolean,
    default: false,
  },
})

const emit = defineEmits<{
  (e: 'update:modelValue', value: number): void
}>()

const add = () => {
  if (props.modelValue >= props.max) return
  emit('update:modelValue', props.modelValue + 1)
}

const sub = () => {
  if (props.modelValue <= props.min) return
  emit('update:modelValue', props.modelValue - 1)
}
</script>
<template>
  <div class="numbox">
    <div class="label" v-if="showLabel"><slot>数量</slot></div>
    <div class="numbox">
      <a href="javascript:;" @click="sub">-</a>
      <input type="text" readonly :value="modelValue"/>
      <a href="javascript:;" @click="add">+</a>
    </div>
  </div>
</template>

<style scoped lang="less">
.numbox {
  display: flex;
  align-items: center;
  .label {
    width: 60px;
    color: #999;
    padding-left: 10px;
  }
  .numbox {
    width: 120px;
    height: 30px;
    border: 1px solid #e4e4e4;
    display: flex;
    > a {
      width: 29px;
      line-height: 28px;
      text-align: center;
      background: #f8f8f8;
      font-size: 16px;
      color: #666;
      &:first-of-type {
        border-right: 1px solid #e4e4e4;
      }
      &:last-of-type {
        border-left: 1px solid #e4e4e4;
      }
    }
    > input {
      width: 60px;
      padding: 0 5px;
      text-align: center;
      color: #666;
    }
  }
}
</style>

动态控制禁用效果

<script lang="ts" setup name="Numbox">
const props = defineProps({
  modelValue: {
    type: Number,
    default: 1,
  },
  min: {
    type: Number,
    default: 1,
  },
  max: {
    type: Number,
    default: 20,
  },
  showLabel: {
    type: Boolean,
    default: false,
  },
})

const emit = defineEmits<{
  (e: 'update:modelValue', value: number): void
}>()

const add = () => {
  if (props.modelValue >= props.max) return
  emit('update:modelValue', props.modelValue + 1)
}

const sub = () => {
  if (props.modelValue <= props.min) return
  emit('update:modelValue', props.modelValue - 1)
}
</script>
<template>
  <div class="numbox">
    <div class="label" v-if="showLabel"><slot>数量</slot></div>
    <div class="numbox">
     + <a href="javascript:;" @click="sub" :class="{not:props.modelValue <= props.main}">-</a>
      <input type="text" readonly :value="modelValue" />
     + <a href="javascript:;" @click="add" :class="{not:props.modelValue >= props.max}">+</a>
    </div>
  </div>
</template>

<style scoped lang="less">
.numbox {
  display: flex;
  align-items: center;
  .label {
    width: 60px;
    color: #999;
    padding-left: 10px;
  }
  .numbox {
    width: 120px;
    height: 30px;
    border: 1px solid #e4e4e4;
    display: flex;
    > a {
      width: 29px;
      line-height: 28px;
      text-align: center;
      background: #f8f8f8;
      font-size: 16px;
      color: #666;
 +     &.not {
 +       cursor: not-allowed;
 +     }
      &:first-of-type {
        border-right: 1px solid #e4e4e4;
      }
      &:last-of-type {
        border-left: 1px solid #e4e4e4;
      }
    }
    > input {
      width: 60px;
      padding: 0 5px;
      text-align: center;
      color: #666;
    }
  }
}
</style>

使用组件：src/views/goods/index.vue

<script lang="ts" setup name="Numbox">
import {ref} from "vue";
    
const count = ref(1)
</script>

<!-- 商品信息 -->
<div class="goods-info">
    <!-- 数字选择框 -->
    <XtxNumbox v-model="count" min:"1" :max="20" ></XtxNumbox>
</div>

思考：

我们的输入框不仅能点击加减还可以输入数字，如果用户通过输入框输入非数字会出现什么问题?

优化代码

<script lang="ts" setup name="Numbox">
const props = defineProps({
  modelValue: {
    type: Number,
    default: 1,
  },
  min: {
    type: Number,
    default: 1,
  },
  max: {
    type: Number,
    default: 20,
  },
  showLabel: {
    type: Boolean,
    default: false,
  },
})
+const { proxy } = getCurrentInstance() as ComponentInternalInstance
const emit = defineEmits<{
  (e: 'update:modelValue', value: number): void
}>()

const add = () => {
  if (props.modelValue >= props.max) return
  emit('update:modelValue', props.modelValue + 1)
}

const sub = () => {
  if (props.modelValue <= props.min) return
  emit('update:modelValue', props.modelValue - 1)
}
   
+const handleChange = (e: Event) => {
+  // 通过类型断言，让ts知道目前元素的类型
+  const element = e.target as HTMLInputElement
+  let value = +element.value
+  if (isNaN(value)) value = 1
+  if (value >= props.max) value = props.max
+  if (value <= props.main) value = props.main
+  emit('update:modelValue',value)
  
+  // 强制刷新
+  proxy?.$forceUpdate()
}    
</script>
<template>
  <div class="numbox">
    <div class="label" v-if="showLabel"><slot>数量</slot></div>
    <div class="numbox">
      <a href="javascript:;" @click="sub" :class="{not:props.modelValue <= props.main}">-</a>
      <input type="text" readonly :value="modelValue" @change="handleChange($event)"/>
      <a href="javascript:;" @click="add" :class="{not:props.modelValue >= props.max}">+</a>
    </div>
  </div>
</template>

<style scoped lang="less">
.numbox {
  display: flex;
  align-items: center;
  .label {
    width: 60px;
    color: #999;
    padding-left: 10px;
  }
  .numbox {
    width: 120px;
    height: 30px;
    border: 1px solid #e4e4e4;
    display: flex;
    > a {
      width: 29px;
      line-height: 28px;
      text-align: center;
      background: #f8f8f8;
      font-size: 16px;
      color: #666;
      &.not {
        cursor: not-allowed;
      }
      &:first-of-type {
        border-right: 1px solid #e4e4e4;
      }
      &:last-of-type {
        border-left: 1px solid #e4e4e4;
      }
    }
    > input {
      width: 60px;
      padding: 0 5px;
      text-align: center;
      color: #666;
    }
  }
}
</style>