Question

我想解决以下问题：在通过angularfire从Firestore中获取了一个集合之后，我想遍历这些集合中的每个文档，然后执行一个单独的Firestore请求，以获取一个相应的文档，在返回该集合之前，我要将这些值插入第一个文档中。

例如，有一个名为ball的对象，具有属性

interface Ball: {
  uid: string; 
  color: string;
}

还有具有属性

的对象player

interface Player: {
  uid: string;
  correspondingBall: ball;
}

在Firestore集合中，我保存了Player类型的文档，并从相应的球中保存了相应的ID（希望您知道我的意思）。现在，我访问收藏夹播放器

getRecentPlayers(): Observable<Player[]> {
    const players: AngularFirestoreCollection<any> = this.angularFirestore.collection<Player>('players');
    return players ? players.snapshotChanges().pipe(
      map(players => {
        return players.map(player => {
          const data = player.payload.doc.data() as Player;
          const correspondingBall: AngularFirestoreDocument<Ball> = this.angularFirestore.doc('balls/' + data.correspondingBall);
          correspondingBall ? correspondingBall.snapshotChanges().pipe(
            map(ball => {
              const data = ball.payload.data() as Ball;
              return data;
            })
          ) : null;
          return {...data, correspondingBall}
        })
      })
    ) : null;
  }

那样，我不会工作。有人能帮我吗？非常感谢你！

Answer 1

通常的方式是：进行咨询（返回值数组），进行switchMap，创建可观察对象数组，进行forkjoin，使用索引进行映射以添加新属性。我用简单的gets去编码

getPlayers().pipe(
  switchMap(players=>{
    //in players we has an array of player
    //create an array of observables with the array
    const obs=players.map(player=>getBall(player.ballId)
    //a switchMap must return an observable, so return a forkJoin
    return forkjoin(obs).pipe(
       //but we transform the result that is an array
       //with the values of getBall(1),getBall(2)..
       map((ball,index)=>{
          //concat the properties of players[index] with the ball
          return {...players[index],..ball}
       })
    )
  }
)).subscribe(res=>console.log(res))

返回之前如何在文档中添加对象？

1 个答案: