<input v-model="tab">

<input :value="tab" :input="tab = $event.target.value">

<Tab v-model="tab"></Tab>

<!-- Tab.vue -->
<template>
 <div class="tab">
  <p>可以试着把这个值打印出来😀😀😀</p>
  {{value}}
 </div>
</template>


<script>
 export default {
  props: {
   // ↓这个就是我们能取到的参数
   value: {
    type: String,
    default: ''
   }
  }
 }
</script>

<!-- example.vue -->
<template>
 <div>
  <!-- 这里多了一个参数 ↓ -->
  <Tab v-model="tab" :options="options"></Tab>
  <p class="info">{{tab}}</p>
 </div>
</template>

<script>
 import Tab from '~/Tab';

 export default {
  components: {
   Tab
  },
  data() {
   return {
    tab: 'bj',
    options: [{
     value: 'bj',
     text: '北京'
    }, {
     value: 'sh',
     text: '上海',
     disabled: true
    }, {
     value: 'gz',
     text: '广州'
    }, {
     value: 'sz',
     text: '深圳'
    }]
   }
  }
 }
</script>

<!-- Tab.vue -->
<template>
 <div class="tab">
  <div 
   class="item"
   v-for="(item, i) in options"
   :key="i">
   {{item.text}}
  </div>
 </div>
</template>

<script>
 export default {
  props: {
   value: {
    type: String
   },
   options: {
    type: Array,
    default: []
   }
  }
 }
</script>

<!-- Tab.vue -->
<script>
 export default {
  props: {
   value: {
    type: String
   },
   options: {
    type: Array,
    default: []
   }
  },
  data() {
   return {
    // 拷贝一个 value
    currValue: this.value,
    currOptions: []
   }
  },
  mounted() {
   this.initOptions();
  },
  methods: {
   initOptions() {
    // 拷贝一个 options
    this.currOptions = this.options.map(item => {
     return {
      ...item,
      active: item.value === this.currValue,
      disabled: !!item.disabled
     }
    });
   }
  }
 }
</script>

<!-- Tab.vue -->
<template>
 <div class="tab">
  <div 
   class="item"
   v-for="(item, i) in options"
   :key="i"
   @click="onTabSelect(item)">
   <!-- ↑ 这里绑定了一个事件！ -->
   {{item.text}}
  </div>
 </div>
</template>

<script>
 export default {
  props: {
   value: {
    type: String
   },
   options: {
    type: Array,
    default: []
   }
  },
  data() {
   return {
    currValue: this.value,
    currOptions: []
   }
  },
  mounted() {
   this.initOptions();
  },
  methods: {
   initOptions() {
    this.currOptions = this.options.map(item => {
     return {
      ...item,
      active: item.value === this.currValue,
      disabled: !!item.disabled
     }
    });
   },
   // 添加选中事件
   onTabSelect(item) {
    if (item.disabled) return;
    this.currOptions.forEach(obj => obj.active = false);
    item.active = true;
    this.currValue = item.value;
    // 发布 input 事件，↓ 父组件如果有 v-model 就会监听到的。
    this.$emit('input', this.currValue);
   }
  }
 }
</script>

<!-- example.vue -->
<template>
 <div>
  <Tab v-model="tab" :options="options"></Tab>
  <p class="info">{{tab}}</p>
 </div>
</template>

<script>
 import Tab from '~/Tab';

 export default {
  components: {
   Tab
  },
  data() {
   return {
    tab: 'bj',
    options: [{
     value: 'bj',
     text: '北京'
    }, {
     value: 'sh',
     text: '上海',
     disabled: true
    }, {
     value: 'gz',
     text: '广州'
    }, {
     value: 'sz',
     text: '深圳'
    }]
   }
  }
 }
</script>

<style lang="less" scoped>
 .info {
  margin-left: 50px;
  font-size: 30px;
 }
</style>

<!-- Tab.vue -->
<template>
 <div class="tab">
  <div 
   class="item"
   v-for="(item, i) in currOptions"
   :class="item | tabItemClass"
   :key="i"
   @click="onTabSelect(item)">
   {{item.text}}
  </div>
 </div>
</template>

<script>
 export default {
  props: {
   value: {
    type: String
   },
   options: {
    type: Array,
    default: []
   }
  },
  data() {
   return {
    currValue: this.value,
    currOptions: []
   }
  },
  mounted() {
   this.initOptions();
  },
  methods: {
   initOptions() {
    this.currOptions = this.options.map(item => {
     return {
      ...item,
      active: item.value === this.currValue,
      disabled: !!item.disabled
     }
    });
   },
   onTabSelect(item) {
    if (item.disabled) return;
    this.currOptions.forEach(obj => obj.active = false);
    item.active = true;
    this.currValue = item.value;
    this.$emit('input', this.currValue);
   }
  },
  filters: {
   tabItemClass(item) {
    let classList = [];
    if (item.active) classList.push('active');
    if (item.disabled) classList.push('disabled');
    return classList.join(' ');
   }
  },
  watch: {
   options(value) {
    this.initOptions();
   },
   value(value) {
    this.currValue = value;
   }
  }
 }
</script>

<style lang="less" scoped>
 .tab {
  @borderColor: #ddd;
  @radius: 5px;

  width: 100%;
  margin: 50px;
  overflow: hidden;
  position: relative;
  .item {
   padding: 10px 50px;
   border-top: 1px solid @borderColor;
   border-left: 1px solid @borderColor;
   border-bottom: 1px solid @borderColor;
   font-size: 30px;
   background-color: #fff;
   float: left;
   user-select: none;
   cursor: pointer;
   transition: 300ms;
   &:first-child {
    border-top-left-radius: @radius;
    border-bottom-left-radius: @radius;
   }
   &:last-child {
    border-right: 1px solid @borderColor;
    border-top-right-radius: @radius;
    border-bottom-right-radius: @radius;
   }
   &.active {
    color: #fff;
    background-color: red;
   }
   &:hover {
    color: #fff;
    background-color: #f06;
   }
   &.disabled {
    color: #fff;
    background-color: pink;
    cursor: no-drop;
   }
  }
 }
</style>