Question:

**Error: InvalidPipeArgument: '[object Object]' for pipe 'AsyncPipe'. **

I am trying to do unsubscribe the observable

Angular-cli = 6.0.3

<blockquote>

HTML home.component.html

</blockquote> <div class="starter-template">

<ul> <li *ngFor="let course of courses$ | async"> {{ course.$value }} </li> </ul> </div> <blockquote>

Typescript home.component.ts

</blockquote> export class HomeComponent { courses$; constructor(db: AngularFireDatabase) { this.courses$ = db.list('/course'); } }

The doc (<a href="https://github.com/angular/angularfire2/blob/master/docs/rtdb/lists.md#retrieve-data" rel="nofollow">https://github.com/angular/angularfire2/blob/master/docs/rtdb/lists.md#retrieve-data</a>) says you need to use .valueChanges():

import { Component } from '@angular/core'; import { AngularFireDatabase } from 'angularfire2/database'; import { Observable } from 'rxjs'; @Component({ selector: 'app-root', template: ` <ul> <li *ngFor="let item of items | async"> {{ item | json }} </li> </ul> `, }) export class AppComponent { items: Observable<any[]>; constructor(db: AngularFireDatabase) { this.items = db.list('items').valueChanges(); } }