ref.ts

export class DocRef {
  private ref: firebase.firestore.DocumentReference;
  private stream;

  constructor(private path: string) {
    this.ref = firebase.firestore().doc(path);
    this.stream = Observable.create(observer => {
      this.ref.onSnapshot({
        next(doc) {
          observer.next(doc);
        }
      });
    }).pipe(shareReplay(1));
  }

  snapshot() {
    return this.stream;
  }

  data() {
    return this.stream.pipe(map(v => (v as any).data()));
  }

  update(data) {
    return from(this.ref.update(data));
  }
  
  log() {
    this.stream.subscribe(x => console.log('doc read') )
  }
}

usage.ts

const elephant = rxfire.ref('animals/elephant');

ref.snapshot().subscribe(console.log);

ref.data().subscribe(console.log);


// Multiple subscribers, all sharing one doc read
ref.data().subscribe(console.log);