如何从 angular 中的 firebase 中的实时数据库接收数据

Question

I want to receive data from the realtime database in firebase. The Data is shown below:

The code I tried is

return this.db.list('messages', ref => {
  return ref.limitToLast(25).orderByKey();
});

but it's not working

Answer 1

Try this to get the messages list from the firestore. Import AngularFireDatabase service and AngularFireList to store message collection.

 import { Injectable } from '@angular/core'; import { AngularFireDatabase, AngularFireList } from '@angular/fire/database'; @Injectable({ providedIn: 'root' }) export class MessageService { messages: AngularFireList<any>; constructor(private http: HttpClient, private db: AngularFireDatabase) { } /** * Get All tickers from firebase */ getMessages(): Observable<any> { this.messages = this.db.list('messages'); return this.messages.valueChanges(); } }

Make sure you have imported AngularFireModule and AngularFireDatabaseModule in your app module.

Answer 2

AngularFire is build with the Observable Pattern via RxJs Library.

You can stream the data with the valueChanges() method, as described in the documentation

items: Observable<any[]>;
constructor(firestore: AngularFirestore) {
   this.items = firestore.collection('items').valueChanges();
}