angular-docs-cn/aio/content/examples/toh-pt5/src/app/messages/messages.component.html

<div *ngIf="messageService.messages.length">

  <h2>Messages</h2>
  <button class="clear"
          (click)="messageService.clear()">clear</button>
  <div *ngFor="let message of messageService.messages"> {{message}} </div>

</div>