Question

我具有以下功能

getParticipations(
    meetingId: string
  ): Observable<Participation[]> {
    return this.meetingCollection
      .doc(meetingId)
      .collection<ParticipationDto>('participations')
      .snapshotChanges()
      .pipe(
        map(actions =>
          actions.map(m => {
            const participationDto = m.payload.doc.data() as ParticipationDto;
            const id = m.payload.doc.id;
            return new Participation(id, participationDto.vart, null);
          })
        )
      );
  }

在participationDto中有一个文档引用，我想获取该文档，以便返回带有引用文档映射的对象（参与）。

类似

  getParticipations(
    meetingId: string
  ): Observable<Participation[]> {
    return this.meetingCollection
      .doc(meetingId)
      .collection<ParticipationDto>('participations')
      .snapshotChanges()
      .pipe(
        map(actions =>
          actions.map(m => {
            const participationDto = m.payload.doc.data() as ParticipationDto;
            const id = m.payload.doc.id;
            return this.participantCollection.doc(participationDto.participant.id).get().pipe(
              map(pp => {
                return new Participation(id, participationDto.vart, pp.data() as Participant);
              })
            );
          })
        )
      );
  }

但是它返回一个Observable<Observable<Participation>[]> 我可能需要合并，映射或类似方法，但是我找不到正确的方法来丰富我的Observable对象映射并保持我的Observable<Participation[]>

感谢帮助

Answer 1

您可以尝试在Observables的内部列表上使用forkJoin并将外部地图切换到switchMap。

     getParticipations(
    meetingId: string
  ): Observable<Participation[]> {
    return this.meetingCollection
      .doc(meetingId)
      .collection<ParticipationDto>('participations')
      .snapshotChanges()
      .pipe(
        switchMap(actions =>
          forkJoin(actions.map(m => {
            const participationDto = m.payload.doc.data() as ParticipationDto;
            const id = m.payload.doc.id;
            return this.participantCollection.doc(participationDto.participant.id).get().pipe(
              map(pp => {
                return new Participation(id, participationDto.vart, pp.data() as Participant);
              })
            ));
          })
        )
      );
  }

Answer 2

您需要使用mergeMap代替map

类似下面的

getParticipations(
    meetingId: string
  ): Observable<Participation[]> {
    return this.meetingCollection
      .doc(meetingId)
      .collection<ParticipationDto>('participations')
      .snapshotChanges()
      .pipe(
        mergeMap(actions =>
          actions.map(m => {
            const participationDto = m.payload.doc.data() as ParticipationDto;
            const id = m.payload.doc.id;
            return this.participantCollection.doc(participationDto.participant.id).get().pipe(
              map(pp => {
                return new Participation(id, participationDto.vart, pp.data() as Participant);
              })
            );
          })
        )
      );
  }


getParticipations(
    meetingId: string
  ): Observable<Participation[]> {
    return this.meetingCollection
      .doc(meetingId)
      .collection<ParticipationDto>('participations')
      .snapshotChanges()
      .pipe(
        map(actions =>
          actions.map(m => {
            const participationDto = m.payload.doc.data() as ParticipationDto;
            const id = m.payload.doc.id;
            return this.participantCollection.doc(participationDto.participant.id).get().pipe(
              mergeMap(pp => {
                return new Participation(id, participationDto.vart, pp.data() as Participant);
              })
            );
          })
        )
      );
  }

（由于它是复杂且嵌套的，没有提供stackblitz，因此我无法验证该解决方案，但是如果无法解决，请告诉我删除此答案）

带有子查询的AngularFireStore返回集合

2 个答案: