angularfire2快照数据

Question

我刚开始接触angularfire 2并遇到问题。我有一套餐厅存放在firebase的cloudflare中。我能够正确获取餐馆列表并显示它，但是当我尝试访问并将特定餐馆保存到单独的变量时，它会返回一个我无法从以下数据中获取数据的observable：

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]);
}

组件代码

constructor(private restService: RestaurantService){}

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

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

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

我很难理解如何从firebase中返回的Observable列表中提取数据。

Answer 1

如果要获取Observable的“当前值”，则应使用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
}