vue this.$refs.xxx获取dom注意事项 v-if v-for渲染的dom不能直接使用

<div class="searchWrap">
  <div class="searchItem" v-for="(tag, tagIndex) in pinPaiList" :key="tagIndex">
    <div class="searchLeft">{{ tag.tagSortTitle }}</div>
    <div class="searchList" :ref="'tagParent' + tagIndex">
      <div v-for="(p, pIndex) in tag.items" :key="pIndex" class="listCls">
        <span @click="selectPP(tagIndex, pIndex)" :class="{ active: p.checked }">{{ p.value | filterStr }}</span></div></div>
    <div class="searchMore">
      <div>
       	<div class="el-icon-arrow-down" v-if="tag.moreFlag" @click="moreData(tagIndex)">更多</div>
        <div class="el-icon-circle-check" v-if="tag.selectMore" @click="sureSearch(tagIndex)"
          :class="{ active: tag.selectMore }" >确定</div>
        <div @click="changeType(tagIndex)" :class="{ active: tag.selectMore }" class="el-icon-circle-plus-outline">{{ !tag.selectMore ? "单选" : "多选" }}
        </div>
      </div>
    </div>
  </div>
</div>

:ref="'tagParent' + tagIndex"

...
//此处的this.pinPaiList是从上面的接口中获取到的数据，需要循环遍历，依次判断高度
this.pinPaiList && this.pinPaiList.forEach((p, pIndex) => {
   this.$nextTick(() => {
   //一定要注意通过this.$refs.xxx的方式获取到的dom要取index为0的一项，然后获取高度通过clientHight来获取，如果不是v-if或者v-for渲染的dom，则不需要加这个0。
     var height = this.$refs[`tagParent${pIndex}`][0].clientHeight;
     if (height > 50) {
       this.pinPaiList[pIndex].moreFlag = true;
       //如果判断出来某一项的高度超出一行，则延迟将此行的高度设置为一行，进而展示更多按钮，点击更多按钮时将height改为auto即可
       setTimeout(() => {
         this.$refs[`tagParent${pIndex}`][0].style.height = "35px";
       }, 0);
     } else {
       this.pinPaiList[pIndex].moreFlag = false;
     }
     this.$set(this.pinPaiList, pIndex, this.pinPaiList[pIndex]);
   });
 });
...
//点击更多按钮
moreData(index) {
  this.pinPaiList[index].moreFlag = false;
  this.$set(this.pinPaiList, index, this.pinPaiList[index]);//这个是vue2的缺陷，数据改变视图不渲染的解决方案
  setTimeout(() => {
    this.$refs[`tagParent${index}`][0].style.height = "auto";
  }, 0);
}