情况：我正在使用FirebaSEObjectObservable来填充我的Ionic 2(rc0)模板.
模板代码：
模板代码：
<ion-card-content>
<p>{{(course | async)?.description}}</p>
<br>
<h2>Learning Objectives</h2>
<ul>
<li *ngFor = "let objective of (course | async)?.objectives">{{objective.text}}</li>
</ul>
<h2>Takeaway</h2>
<ul>
<li *ngFor = "let takeaway of (course | async)?.takeaways">{{takeaway.text}}</li>
</ul>
</ion-card-content>
TS代码：
this.course = this.af.database.object('/bbwLocations/courses/' + courseId);
this.course是Firebase Object Observable.一切正常！但每当我进入模板时,都会出现空白无数据.然后所有的数据跳出来！非常友好的UX.所以我想使用某种预加载策略.但由于这里没有TS逻辑.使用异步管道在模板级别控制所有内容.在这种情况下如何添加加载？
解决方法
你可以这样做：
<style>
pre {
color: orange;
// or whatever you want
}
</style>
<ion-card-content>
<p>{{(course | async)?.description}}</p>
<br>
<h2>Learning Objectives</h2>
<pre *ngIf="!(course | async)">loading objectives...</pre>
<ul>
<li *ngFor = "let objective of (course | async)?.objectives">{{objective.text}}</li>
</ul>
<h2>Takeaway</h2>
<pre *ngIf="!(course | async)">loading takeaways...</pre>
<ul>
<li *ngFor = "let takeaway of (course | async)?.takeaways">{{takeaway.text}}</li>
</ul>
</ion-card-content>
