获取下拉框key和value

更新写法：ref=“”

     el-form-item label="杆塔编号" prop="gtbh">
          <el-select v-model="form.towerName" filterable size="medium" clearable placeholder="请选择杆塔编号" ref="ganta" >
            <el-option v-for="(item,index) in gtbhOptions" :key="index" :label="item.objOrder" :value="item.objId"></el-option>
          </el-select>
    </el-form-item>  

取值：

        this.form.towerId=this.$refs.ganta.selectedLabel;
        this.form.lineName=this.$refs.line.selectedLabel;

写法一：

<el-form-item label="所属线路" label-width="120px">
   <el-select v-model="form.lineId" placeholder="所属线路" @change="queryTower" clearable>
      <el-option v-for="(item,index) in allxlist" :key="index" :label="item.lineName" :value="item.obiId"></el-option>
    </el-select>
</el-form-item>

  queryTower (val) {
      this.form.lineName = this.allxlist.filter(item => item.obiId === val)[0].lineName;
      this.allgtList = [];
      this.axios.post("/mXttzGtrunDatas/queryTower", { lineId: [val] }
      ).then(({ data }) => {
        this.allgtList = data.resultValue;
      })
    },

写法二：

 <el-form-item label="所属杆塔" label-width="120px">
    <el-select v-model="form.towerName" placeholder="所属杆塔" @change="towChange" clearable>
          <el-option v-for="(item,index) in allgtList" :key="index" :label="item.objOrder" :value="item.objId"></el-option>
        </el-select>
</el-form-item>

  towChange (val) {
    let choosenItem = this.allgtList.filter(item => item.objId === val);
    this.form.towerName = choosenItem[0].objId;
    this.form.towerId = choosenItem[0].objOrder;
  },