angular/fire 使用 startAfter 获取集合中的下一项

Question

获取集合中的下一项时遇到了真正的问题

我得到的错误是：

Error: Function startAfter() called with invalid data. Unsupported field value: a custom AngularFirestoreDocument object

基于这些 Firebase docs I think startAfter() wants a DocumentSnapshot but I don't know how to convert AngularFirestoreDocument to DocumentSnapshot and whilst the angular/fire docs 提及 startAfter 他们没有给出任何代码示例。

这是我的问题代码。我想要集合中 video 文档之后的第一个文档。

getNextVideo$(id: string, group: string): Observable<IVideo> {

  const video: AngularFirestoreDocument<IVideo> = this.afs.doc<IVideo>(`videos/${id}`)

  const collection: AngularFirestoreCollection<IVideo> = this.afs.collection<IVideo>('videos', ref => {
    return ref
      .where('group', '==', group)
      .where('flowPlayerProcessed', '==', true)
      .orderBy('timeCreated')
      .startAfter(video) // <<<<< ERROR IS HERE
      .limit(1)
  })

  return collection.valueChanges().pipe(
    map((videos: IVideo[]) => videos.length ? videos[0] : null)
  )
}

提前致谢

Answer 1

好的，这个相当冗长的怪物有效

getNextVideo$(id: string, group: string): Observable<IVideo> {

  const video: AngularFirestoreDocument<IVideo> = this.afs.doc<IVideo>(`videos/${id}`)

  return video.snapshotChanges().pipe(
    switchMap((videoSnapshotAction: Action<DocumentSnapshot<IVideo>>) => {

      const videoSnapshot: DocumentSnapshot<IVideo> = videoSnapshotAction.payload

      const collection: AngularFirestoreCollection<IVideo> = this.afs.collection<IVideo>('videos', ref => {
        return ref
          .where('group', '==', group)
          .where('flowPlayerProcessed', '==', true)
          .orderBy('timeCreated')
          .startAfter(videoSnapshot)
          .limit(1)
      })
      return collection.valueChanges().pipe(
        map((videos: IVideo[]) => videos.length ? videos[0] : null)
      )
    })
  )
}

angular/fire 使用 startAfter 获取集合中的下一项

angular/fire get next item in collection using startAfter

angular

firebase

angularfire2