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"  
  }
 ]
 }
 ]
 }
]