AngularFire2: Realtime Database: how to get key and value

Question

I use AngularFire2 to get data from Firebase Database (realtime).

What I have done:

• Firebase Database

{ “class” : { “student” : { “Tom” : “male”, “Mary” : “female”, “Peter” : “male”, “Laura” : “female” }, "numberOfStudent” : 10 } }

• app.component.ts

  import { AngularFireDatabase } from 'angularfire2/database';
  import { Observable } from 'rxjs/Observable';
  
  ...
  export class AppComponent {
  
     class: Observable<any>;
     students: Observable<any[]>;
  
  constructor(private db: AngularFireDatabase) {
     this.class = db.object(‘class’).valueChanges();
     this.students = db.list(‘class/student’).snapshotChanges();
   }
  
  } 
  

• app.component.html:

<h2>Class size: {{ (class | async)?.numberOfStudent }}</h2>
<ul>
  <li *ngFor="let i of students | async">
    {{i.key}} : {{i.value}}
  </li>
</ul>

What happened:

Class size: 10

Tom :

Mary :

Peter :

Laura :

It doesn't return the value of list.

Any suggestion is appreciated.

Answer 1

UPD

with new Angular 6 and RxJS 6 you'll do this:

import { map } from 'rxjs/operators';
// ...
return this.fb.list(`/path/to/list`)
  .snapshotChanges()
  .pipe(map(items => { .            // <== new way of chaining
    return items.map(a => {
      const data = a.payload.val();
      const key = a.payload.key;
      return {key, data};           // or {key, ...data} in case data is Obj
    });
  }));

Answer 2

I managed to get the key and value of list. Just follow some tips below:

• Make sure using snapshotChanges()

<li *ngFor="let i of seats | async">
    {{i.key}} : {{i.payload.val()}}
</li>

It worked for me, but I am still opening to receive more best practices