How to JOIN two nodes with AngularFire2 and Firebase?

问题

I have this structure of my Firebase Database

Each library can have several albums. How can I display the albums for each library?

the albumsPerLib: first element is the library key, and underneath each library key, I store the albums keys, that belong to it.

But I'm not used to NoSQL and can't figure how to join the tables to display the albums for each library.

回答1:

so this works:

  getAlbumsThatBelongToLib(libKey:string):Observable<Album[]>{
//get the keys for the lib albums
const albumsPerLib$ = this.db.list(`albumsPerLib/${libKey}`);

//map the returned list of keys
//and get their details from the albums node
return albumsPerLib$
  .map((albumKeys) => albumKeys
      .map( (albumKey) => {
         return this.db.object(`albums/${albumKey.$key}`)
      }))
  .flatMap((res) => {
    return Observable.combineLatest(res);
  });
}

来源：https://stackoverflow.com/questions/40999531/how-to-join-two-nodes-with-angularfire2-and-firebase