记一次v-if失效的经历

一个很低级的错误。
背景：点击学生信息，学生信息的具体内容收起，右上角的icon改变。

        <div class="panel panel-info">
            <div class="panel-heading" @click="shrink()">
                <el-row :gutter="20">
                    <el-col :span="23"><span class="panel-title">学生信息</span></el-col>
                    <el-col :span="1"><b-icon v-if="!activeStudent" icon="arrow-right" key="1"></b-icon></el-col>
                    <el-col :span="1"><b-icon v-if="activeStudent" icon="arrow-down" key="2"></b-icon></el-col>
                </el-row>
            </div>
            <table class="table" v-show="activeStudent">
                <tr>
                    <th>学号</th>
                    <th>姓名</th>
                    <th>班级</th>
                </tr>
                <tr v-for="(studentItem,index) in studentData" :key="index">
                    <td  v-for="(item,idx) in studentItem" :key="idx">
                        {{item}}
                    </td>
                </tr>
            </table>
        </div>

js部分注意是data而不是computed！ 如果是computed就无法实现！

 data(){
            return{
                //折叠面板的序号
                activeStudent: false,
                }
      }