vue2.0 element-ui中el-select选择器无法显示选中的内容(解决方法)

<template>
 <div>
 <div class="row" v-for="RowItem in rows">
  <div class="col" v-for="colItem in RowItem.configVos">
  <el-select v-model="formData[colItem.paramCode]" :class="getModel(colItem.paramCode)" @change="onSelectChange(colItem.paramCode,formData[colItem.paramCode])">
   <el-option v-for="option in colItem.configOptions" :label="option.optionCode" 
   :value="option.optionValue" >
   </el-option>
 </el-select>
  </div> 
 </div> 
 </div> 
</template>
<script>
 import axios from 'axios';
 export default {
 data() {
  return {
  groupItem:{},
  formData:{},
  rows:'',
  cols:''
  }
 },
 watch:{
 },
 methods:{  
  getfordata:function(){
  var _this = this;
  axios.get('../json/selectdata.json')
  .then(function(res){
   _this.groupItem = res.data;
   var row = _this.groupItem[0].rowData;
   _this.rows = row;  
   for(var i=0;i<row.length;i++){
   var col = row[i].configVos;   
   for(var j=0;j<col.length;j++){ 
    var key = col[j];    
    _this.formData[key.paramCode] = '';  
   }
   }   
  })
  },
  onSelectChange:function(key,val){
  console.log(val);
  },
  getModel(model) {
  console.log(model);
  }
 },
 created:function(){
  this.getfordata();
 }
 }
</script>
<style scoped>
 .col{
 float:left;
 }
 .row{
 width:800px;
 height:100px;
 }
</style>

[
 {
 "groupName": "抽数转换",
 "rowData": [
 {
 "configVos": [
  {
  "configOptions": [
  {
  "id": "D",
  "optionCode": "否",
  "optionValue": "0",
  "paramId": "4"
  },
  {
  "id": "5",
  "optionCode": "是",
  "optionValue": "1",
  "paramId": "4"
  }
  ],
  "id": "4E",
  "paramCode": "isView",
  "paramValue": "0"
  },
  {
  "configOptions": [
  {
  "id": "4",
  "optionCode": "老版本",
  "optionValue": "0",
  "paramId": "4"
  },
  {
  "id": "4",
  "optionCode": "新版本",
  "optionValue": "1",
  "paramId": "44"
  }
  ],
  "id": "24",
  "paramCode": "isDeleteCbnd",
  "paramValue": "1"
  }
 ]
 },
 {
 "configVos": [
  {
  "configOptions": [
  {
  "id": "EF",
  "optionCode": "估值2.5",
  "optionValue": "0",
  "paramId": "1"
  },
  {
  "id": "8B",
  "optionCode": "估值2.5+qd",
  "optionValue": "1",
  "paramId": "131"
  },
  {
  "id": "06",
  "optionCode": "恒生2.5",
  "optionValue": "2",
  "paramId": "1"
  },
  {
  "id": "25BF",
  "optionCode": "估值4.5",
  "optionValue": "3",
  "paramId": "31"
  }
  ],
  "id": "31",
  "paramCode": "converType",
  "paramValue": "0"
  },
  {
  "configOptions": [
  {
  "id": "1366",
  "optionCode": "万德",
  "optionValue": "0",
  "paramId": "98"
  },
  {
  "id": "EC",
  "optionCode": "聚源",
  "optionValue": "1",
  "paramId": "8"
  }
  ],
  "id": "91F8",
  "paramCode": "zxDataSource",
  "paramValue": "0"
  }
 ]
 },
 {
 "configVos": [
  {
  "configOptions": [
  {
  "id": "CD",
  "optionCode": "期货占用",
  "optionValue": "HS",
  "paramId": "5C"
  },
  {
  "id": "91508011",
  "optionCode": "其它",
  "optionValue": "YYS",
  "paramId": "91C"
  }
  ],
  "id": "5C",
  "paramCode": "derivativeDataSource",
  "paramValue": "HS"  
  }
 ]
 }
 ]
 }
]