javascript - 如何将 Observable 流转换为 Observable 数组

Question

我正在尝试从数据库中检索狗的列表。我想检索狗的列表为 Observable<Dog[]> 。但是，当我调用 toArray() 或使用任何其他方法尝试将传入流转换为数组时，我在调用 retrieveDogs(dogsId) 时没有收到任何数据。方法。如何检索 Observable array而不仅仅是 Observable stream ？

    retrieveDogs(dogIds : Array<string>): Observable<Dog[]>{
        return Observable.from(dogIds)
                .map(dogId => this.retrieveDog(dogId)) 
                .flatMap(dogObservable => dogObservable)
                .toArray();
     }

    retrieveDog(dogId : string) : Observable<DogEntity> {
     //afDB -> AngularFireDatabase that returns an observable with the data from the firebase database
        return this.afDB.object(DB_DOGS + DB_DASH + dogId)
                .map(dogObject =>DogEntity.convertObject(dogId,dogObject)
    }

Answer 1

您可以这样做来检索您的数据:

retrieveDogs(dogIds : Array<string>): Observable<Dog[]>{
  let obs = dogIds.map(dogId => this.retrieveDog(dogId));

  return Observable.forkJoin(obs);
}

retrieveDog(dogId : string) : Observable<DogEntity> {
  return this.afDB.object(DB_DOGS + DB_DASH + dogId)
    .map(dogObject => DogEntity.convertObject(dogId,dogObject));
}

这里有简单的演示 http://jsbin.com/sotunopocu/2/edit?js,console