获取项目长度ngfor async/observable<aviso[]>;

在角4中,可以这样做:

*ngFor="let aviso of avisosTest | async as aviso; let i = index"

然后你可以打电话 {{ avisosTest.length }} 在那个标签里面。

例子

<ul>
  <li *ngFor="let aviso of avisosTest | async as aviso; let i = index">
    {{aviso}} - {{i + 1}} of {{aviso.length}}
  </li>
</ul>

Working Demo -等待2秒钟以加载数据

如果你需要它在循环之外,你可以分开 async 和 ngFor ,比如:

<div *ngIf="avisosTest | async as aviso">
  <ul>
    <li *ngFor="let aviso of aviso; let i = index">
      {{aviso}}
    </li>
  </ul>
  <div>
    {{aviso.length}} items total
  </div>
</div>

Working Demo -等待2秒钟以加载数据

我想你需要

<div *ngIf="(avisosTest | async)?.length==0">No records found.</div>

或

<div *ngIf="(avisosTest | async)?.length>0">{{avisosTest.legnth}}</div>