<template>
    <div>
      <input type='checkbox' class='input-checkbox' ：checked="fruitIds.length === fruits.length" @click='checkedAll()'>全選
      <div v-for='(fruit, index) in fruits' :key="index">
          <!--判斷fruitIds是否包含當前fruit，fruitIds.indexOf(fruit.fruitId)返回包含fruit的下標, 若不包含則返回-1-->
         <input type='checkbox' :checked="fruitIds.indexOf(fruit.fruitId)>=0" name='checkboxinput' class='input-checkbox' @click='checkedOne(fruit.id)'>
      </div>
      <!--默認刪除按鈕不能點擊, 當選中某一checkbox時可以刪除-->
      <button :disabled="!fruitIds.length>0" value="Delete" @click="deleteFruits()">Delete</button>
    </div>
</template>

<script>
export default {
  data () {
    return {
      fruits:[{
        id:'1',
        value:'蘋果'
      },{
        id:'2',
        value:'荔枝'
      },{
        id:'3',
        value:'香蕉'
      },{
        id:'4',
        value:'火龍果'
      }],
      fruitIds:['1','3','4'],
      // 初始化全選按鈕, 默認不選
      isCheckedAll: false
    }
  },
  methods:{
    checkedOne (fruitId) {
        let idIndex = this.fruitIds.indexOf(fruitId)
        if (idIndex >= 0) {
          // 如果已經包含了該id, 則去除(單選按鈕由選中變為非選中狀態)
          this.fruitIds.splice(idIndex, 1)
        } else {
          // 選中該checkbox
          this.fruitIds.push(fruitId)
        }
    },
    checkedAll () {
      this.isCheckedAll = !this.isCheckedAll
      if (this.isCheckedAll) {
        // 全選時
        this.fruitIds = []
        this.fruits.forEach(function (fruit) {
          this.fruitIds.push(fruit.fruitId)
        }, this)
      } else {
        this.fruitIds = []
      }
    },
    deleteFruits () {

    }
  }
}
</script>