el-dialog中获取el-table组件的ref值报undefined错误！

clickDialog() {
  this.dialogVisible = true
  //弹窗框全部执行完成后执行下面
  this.$nextTick(() => {
    const thisT = this.$refs.table //放到外层也会报错
    console.log('thisT1', typeof thisT)
    console.log('thisT2', thisT)
  })
}