如何检查可观察数组的长度 [英] How to check the length of an Observable array

问题描述

在Angular 2组件中，我有一个Observable数组

In my Angular 2 component I have an Observable array

list$: Observable<any[]>;

我的模板中有

<div *ngIf="list$.length==0">No records found.</div>

<div *ngIf="list$.length>0">
    <ul>
        <li *ngFor="let item of list$ | async">item.name</li>
    </ul>
</div>

但是list $ .length在Observable数组的情况下不起作用.

But list$.length doesn't work with in case of Observable array.

更新:

似乎(list $ | async)?. length 给了我们长度，但是下面的代码仍然不起作用:

It seems that (list$ | async)?.length gives us the length but the below code still doesn't work:

<div>
    Length: {{(list$ | async)?.length}}
    <div *ngIf="(list$ | async)?.length>0">
        <ul>
            <li *ngFor="let item of (list$ | async)">
                {{item.firstName}}
            </li>
        </ul>
    </div>
</div>

任何人都可以指导我如何检查可观察数组的长度.

Can anyone please guide how do I check length of Observable array.

推荐答案

您可以使用| async管道:

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

更新-Angular版本6:

如果要加载CSS骨架，则可以使用它.如果数组中没有项目，它将显示css模板.如果有数据，请填写ngFor.

If you are loading up a css Skeleton you can use this. If the array has no items it will display the css template. If there is data then fill out the ngFor.

<ul *ngIf="(list$| async)?.length > 0; else loading">
   <li *ngFor="let listItem of list$| async">
      {{ listItem.text }}
   </li>
</ul>

<ng-template #loading>
  <p>Shows when no data, waiting for Api</p>
  <loading-component></loading-component>
</ng-template>

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