背景

簡單做個冒泡排序的效果，vue數(shù)據(jù)交換過后視圖不刷新

demo效果

解決方案總結(jié)

栗子??

<template>
  <div class="bubbling">
    <div class="report">
      <div class="item"
           v-for="(itm, inx) in arr"
           :key="inx"
           :tip="itm"
           :style="{height: itm+'px'}"></div>
    </div>
  </div>
</template>

<script>
import Vue from 'Vue'
export default {
  name: 'bubbling',
  data () {
    return {
      arr: []
    }
  },
  mounted () {
    this.buildArray()
  },
  methods: {
    buildArray () {
      for (let i = 0; i < 10; i++) {
        this.arr.push(parseInt(Math.random() * 90 + 10))
      }
      this.beginSort()
    },
    beginSort () {
      let step = 1
      for (let i = 0; i < this.arr.length; i++) {
        for (let j = 0; j < this.arr.length; j++) {
          step++
          setTimeout(() => {
            if (this.arr[i] < this.arr[j]) {
              let temp = this.arr[i]
              /** 方案1 拆裝箱
               * this.arr[i] = this.arr[j]
               * this.arr[j] = temp
               * this.arr = JSON.parse(JSON.stringify(this.arr))
               */
               // 方案2 vue.set
              Vue.set(this.arr, i, this.arr[j])
              this.$set(this.arr, j, temp)
            }
          }, step * 200)
        }
      }
    }
  }
}
</script>

<style lang="scss" scoped>
.bubbling {
  .report {
    margin: 100px auto;
    display: flex;
    height: 150px;
    width: 460px;
    border-left: 1px solid #666;
    border-bottom: 1px solid #666;
    align-items: flex-end;
    .item {
      width: 40px;
      height: 100px;
      background: #9ee;
      margin-left: 5px;
      text-align: center;
      position: relative;
      transition:all .1s
    }
    .item::before {
      content: attr(tip);
      position: absolute;
      width: 40px;
      height: 20px;
      line-height: 20px;
      left: 0px;
      top: -20px;
      text-align: center;
      font-size: 14px;
      color: #666;
    }
  }
}
</style>

知識點

能觸發(fā)vue視圖更新的方法

push()
pop()
shift()
unshift()
splice() 
sort()
reverse()

無效的

// 直接設(shè)置值
this.arr[index] = value;

根本原因

vue2 是通過defineProperty翔试，進(jìn)行遍歷監(jiān)聽屬性尘颓，所以無法監(jiān)聽到對象的刪除等操作
如下：observe是一個類似的原理實現(xiàn)

const observe = (obj: any) => {
  for (const key in obj) {
    let val = obj[key]
    if (typeof val === 'object' && val != null) {
      observe(val)
    }
    Object.defineProperty(obj, key, {
      get () {
        console.log(key, '讀取', val)
        return val
      },
      set (nVal) {
        if (nVal !== val) {
          console.log(key, '更改', nVal)
          val = nVal
        }
      }
    })
  }
}

const obj = {
  id: 1,
  name: '關(guān)羽',
  age: 22,
  equip: {
    head: '',
    weaponry: '砍柴刀'
  }
}

observe(obj)
obj.equip.weaponry = '青龍偃月刀'
console.log(obj.name)

飲水思源

• Vue-set