从后台获取下拉框数据后，默认展开下拉框

<el-select ref = "selectInput" v-bind:disabled = "searchAddressResult.length==0"  v-model = "selectAddress.netAddress"
	value-key = "id" @change = "handelSelectAddresslActive" placeholder = "请选择局向地址" automatic-dropdown > 
    <el-option v -for = "item in searchAddressResult" :key = "item.id" :label = "item.netAddress" :value = "item" > < /el-option>         
</el-select>

在下拉框中绑定一个ref的名字，加上automatic-dropdown这个属性，然后在请求下拉框数据成功之后，写下面的代码

setTimeout(() = >{
    that.$refs.selectInput.focus();
},
100);