角材料数据表分页未定义

Question

为什么分页不起作用

export class AppComponent implements OnInit {
  title = 'app';
  displayedColumns: string[] = ['position', 'name', 'weight', 'symbol'];
  dataSource = new MatTableDataSource<PeriodicElement>(ELEMENT_DATA);
  @ViewChild(MatPaginator) paginator: MatPaginator;

  ngOnInit() {
     this.dataSource.paginator = this.paginator;
  }

这是我从https://material.angular.io/components/table/overview复制的同一个例子