element-ui中v-model值改變了，界面顯示未變，什么問(wèn)題？

使用vue+element開(kāi)始時(shí)，v-model綁定一個(gè)對(duì)象屬性到select元素值，切換select選項(xiàng)時(shí)，綁定的對(duì)象值改變了，但是界面顯示沒(méi)有變，還是原來(lái)的值所對(duì)應(yīng)的選項(xiàng)名稱(chēng)；

<template>
    <div class="bg-hks-container">
        <div class="bg-hks-conditionbox">
            <el-row :gutter="10">
                <el-col 
                  class="bg-hks-condition-col"
                  :xs="24" :sm="12" :md="8" :lg="6" :xl="4" 
                  v-for="item in conditionitems"
                  :key="item.property"
                  >
                    <div class="bg-hks-condition-itembox">
                        <div class="bg-hks-condition-itemname">{{item.name}}：</div>
                        <el-date-picker
                          size="mini"
                          :placeholder="item.placeholder"
                          :type="item.type"
                          v-model="conditions[item.property]"
                          v-if="item.type==='date'||item.type==='datetime'"
                        >
                        </el-date-picker>   
                        <el-input
                          size="mini"
                          :placeholder="item.placeholder"
                          :type="item.type"
                          v-model="conditions[item.property]"
                          v-if="item.type==='text'"
                        >
                        </el-input>
                        <el-select
                          size="mini"
                          :placeholder="item.placeholder"
                          :type="item.type"
                          v-model="conditions[item.property]"
                          v-if="item.type==='select'"
                        >
                            <el-option
                               v-for="opt in item.options"
                               :key="opt.value"
                               :label="opt.name"
                               :value="opt.value">
                            </el-option>
                        </el-select>
                    </div>
                </el-col>
            </el-row>
        </div>
        <table id="dataTable"></table>
    </div>
</template>
<script>
    export default {
        data(){
            return {
                apis:{},
                conditions:{},
                conditionitems:[]
            }
        },
        created(){
            this.initDataForCreate();
        },
        methods:{
            initDataForCreate(){
                this.apis = this.$store.state.apis;
                this.initCondition();
            },
            initCondition(){
                if(this.apis&&this.apis.hotkeycondition){
                    this.$http.get(this.apis.hotkeycondition)
                    .then(response=>{
                        if(response&&response.data){
                            this.conditionitems = response.data;
                        }else{
                            throw '獲取條件ITEM失?。?;
                        }
                    })
                    .catch(error=>{
                        console.error(error);
                    });
                }else{
                    console.error('獲取接口配置失??！')
                }
            }
        },
        watch:{
            conditionitems(){
                if(this.conditionitems.length>0){
                    this.conditionitems.forEach(item=>{
                        this.conditions[item.property] = item.default;
                        if(item.type==='date'||item.type==='datetime'){
                            let date = new Date(item.default);
                            this.conditions[item.property] = date.toString()==='Invalid Date'
                                                           ? new Date()
                                                           : date;
                        }
                    })
                }
            }
        }
    }
</script>
<style lang="less" scoped>