Vue elementui如何实现表格selection的默认勾选

this.$refs.zttable.toggleRowSelection(this.ZHUANTIList[i]);

    <el-dialog :title="title" :visible.sync="openZtScope" width="600px" append-to-body>
      <el-table ref="zttable" :data="ZHUANTIList" @selection-change="handleZTSelectionChange" style="width:100%;">
        <el-table-column type="selection" width="55" align="center" />
        <el-table-column label="编号" align="center" prop="objectid" />
        <el-table-column label="名称" align="center" prop="name" />
      </el-table>
      <pagination
        v-show="zttotal>0"
        :total="zttotal"
        :page.sync="queryParamsZT.pageNum"
        :limit.sync="queryParamsZT.pageSize"
        @pagination="getZTList"
      />
      <div slot="footer" class="dialog-footer">
        <el-button type="primary" @click="submitZtScope">确 定</el-button>
        <el-button @click="cancelZtScope">取 消</el-button>
      </div>
    </el-dialog>

        this.$nextTick(() => {
 
          for (let i = 0; i < this.ZHUANTIList.length; i++) {
            for (let j = 0; j <this.RoleZTList.length ; j++) {
               //两个数组做比对,选中的做勾选
              if(this.ZHUANTIList[i].objectid==this.RoleZTList[j].zhuantiid)
              {
                this.$refs.zttable.toggleRowSelection(this.ZHUANTIList[i]);
              }
            }
          }
 
        });

getZTList() {
      listZHUANTI(this.queryParamsZT).then(response => {
        this.ZHUANTIList = response.rows;
        this.zttotal = response.total;
        //获取当前role的选中的专题
        this.getRoleZTList(this.curRoleId);
      });
 
    },
    getRoleZTList(roleId){
      listRoleZhuanTi({roleid:roleId}).then(response =>{
         debugger;
         this.RoleZTList = response.rows;
 
        //先显示再改dom,这个必须放在nexttick外面
        this.openZtScope = true;
        this.title = "xxx";
 
        //数据更新之后延迟回调，根据最新数据动态改变dom,必须放到nextTick中
        this.$nextTick(() => {
 
          for (let i = 0; i < this.ZHUANTIList.length; i++) {
            for (let j = 0; j <this.RoleZTList.length ; j++) {
               //两个数组做比对,选中的做勾选
              if(this.ZHUANTIList[i].objectid==this.RoleZTList[j].zhuantiid)
              {
                this.$refs.zttable.toggleRowSelection(this.ZHUANTIList[i]);
              }
            }
          }
 
        });
 
      });
    },