select普通操作 （1）

搜索条件需求：接口入参需要houseId，但是要先选择完楼栋，再选择单元，最后选择房屋

如图，我们还得操作两三次。有点烦。

     <el-form-item label="楼栋" prop="buildingId">
            <el-select v-model="queryParams.buildingId"  @change="handleUnit" filterable placeholder="请选择楼栋" style="width: 180px">
              <el-option
              v-for="item in buildingOptions"
              :key="item.buildingId"
              :label="item.buildingName"
              :value="item.buildingId"
              />
          </el-select>
         </el-form-item>
 

        <el-form-item label="单元" prop="unitId"  v-if="queryParams.buildingId">
          <el-select v-model="queryParams.unitId"     @change="handleHouse"  filterable placeholder="请选择单元" style="width: 180px">
            <el-option
            v-for="item in unitOptions"
            :key="item.unitId"
            :label="item.unitName"
            :value="item.unitId"
            />
          </el-select>
        </el-form-item>


      <el-form-item label="房屋" prop="houseId" v-if="queryParams.unitId">
        <el-select v-model="queryParams.houseId"  filterable placeholder="请选择房屋" style="width: 180px">
          <el-option
          v-for="item in houseOptions"
          :key="item.houseId"
          :label="item.houseName"
          :value="item.houseId"
          />
        </el-select>
      </el-form-item>

cascader操作（2）

父组件

      <my-cascader
            v-model="queryParams.houseId"
            v-if="editCascaderVisible"
            :label="'房屋'"
            :prop="'houseId'"
            ></my-cascader>
        
            <my-cascader
            v-model="queryParams.houseId"
            v-else
            :label="'房屋'"
            :prop="'houseId'"
            ></my-cascader>
 

子组件

<!-- MyCascader.vue -->

<template>
    <el-form-item :label="label" :prop="prop">
      <el-cascader
        ref="cascader"
        :options="options"
        :props="propsfs"
        placeholder="请选择房屋"
        v-model="houseId"
        @change="handleChange"
      ></el-cascader>
    </el-form-item>
  </template>
  
  <script setup>
import useUserStore from '@/store/modules/user'
const userStore = useUserStore()
import { buldingSelect } from "@/api/vae/building";
import { unitSelect } from "@/api/vae/unit";
import { houseSelect } from "@/api/vae/house";
  const props = defineProps({
    // 图片数量限制
    label: {
      type: String,
      default: '',
    },
    prop: {
      type: Object,
      default: '',
    },
    modelValue:{
        type:String,
        default: '',
    }
  });
  const $emits = defineEmits(['update:modelValue'])


  const options=ref([]);
  const label=ref(props.label);
  const prop=ref(props.prop);
  const buildingId=ref('')
  const houseId=ref(props.modelValue)
  const propsfs=ref({
        lazy: true,
        lazyLoad (node, resolve) {
          const { level } = node;
          if(level == 0) {
            buldingSelect({villageId:userStore.villageId}).then(res => {
              const nodes = (res.data || [])
              .map(item => ({
                value: item.buildingId,
                label: item.buildingName,
                leaf: level >= 2
              }));
              resolve(nodes);
            })
          } else if(level == 1) {
            buildingId.value=node.value
            unitSelect({villageId:userStore.villageId,buildingId:node.value}).then(res => {
              const nodes = (res.data || [])
              .map(item => ({
                value: item.unitId,
                label: item.unitName,
                leaf: level >= 2
              }));
              resolve(nodes);
            })
          } else {
            houseSelect({villageId:userStore.villageId,buildingId:buildingId.value,unitId:node.value}).then(res => {
              const nodes = (res.data || [])
              .map(item => ({
                value: item.houseId,
                label: item.houseName,
                leaf: level >= 2
              }));
              resolve(nodes);
            })
          }
        }
  })
  const handleChange = (value) => {
    $emits('update:modelValue',value[value.length-1])
}



  </script>
  

v-if="editCascaderVisible" 加这个是为了重新渲染子组件，因为全局需要切换小区，故此不会触发。再加上v-if就可以重新渲染。

在我的子组件中，当 houseId 的值发生变化时，我使用了 $emits('update:modelValue', value[value.length-1]) 来触发父组件的更新。

为什么要加v-else，如果不弄，搜索条件后边的会往前面挤。