angularfire2快照数据

Question

Iam new to angularfire 2 and having a problem. I have a set of restaurantS stored in the cloudflare of firebase. I am able to get the list of restaurants correctly and display it, but when i try to access and save a particular restaurant to a separate variable, it returns an observable which I cant seem to get the data from:

items: Observable<any[]>;
tester: any[] = [];

private test: AngularFirestoreCollection<any>;
constructor(db: AngularFirestore){
    this.test = db.collection<any>('restaurants')
    // this.items = db.collection('restaurants').valueChanges();
    this.items = this.test.snapshotChanges().map(actions => {
      return actions.map(a => {
        const data = a.payload.doc.data();
        this.tester.push(data); //This returns an observable instead of an array
        const id = a.payload.doc.id;
        return { id, ...data };
      });
    });
}

getRestaurants(){
    return this.items;
}

//Here I want to be able to return the item object
getRestaurant(index){
    console.log(this.tester[i]);
}

Component code

constructor(private restService: RestaurantService){}

restaurants = <any>[];
selectedRestaurant: any;

ngOnInit(){
    this.restaurants = this.restService.getRestaurants()
}

onSelect(index){
    console.log(this.restService.getRestaurant(index));
}

Im struggling to understand how I can extract data from the returned Observable list from firebase.

Answer 1

If you want to get at the "current value" of an Observable, you should use a BehaviorSubject.

restaurants: BehaviorSubject<any[]>;
private test: AngularFirestoreCollection<any>;

constructor(db: AngularFirestore){
    this.test = db.collection<any>('restaurants')
    this.test.snapshotChanges().subscribe(this.restaurants);
}

getRestaurants(){
    return this.restaurants.value();
}

getRestaurant(index){
    return getRestaurants()[index]; //.. or whatever you need
}