角 |订阅多个 observables

Question

我正在尝试创建用户将要参加的活动列表。首先我得到事件键，然后我想做的是订阅每个事件并监听变化。目前只有最后一个事件有效，因为 this.eventRef 在 for 循环中被更改。

eventRef: AngularFireObject<any>


getEvents() {

const eventsGuestsLookup = this.db.object(`eventsGuestsLookup/${this.uid}`).valueChanges()

this.eventsGuestsLookupSub = eventsGuestsLookup
  .subscribe(eventKeys => {

    if (eventKeys) {
      console.log(eventKeys)
      for (const k in eventKeys) {
        if (eventKey.hasOwnProperty(k)) {

          this.eventRef = this.db.object(`events/${k}`)

          console.log(this.eventRef)

          this.eventRef.snapshotChanges().subscribe(action => {

            const key = action.payload.key
            const event = { key, ...action.payload.val() }

           this.makeEvents(event)

          })
        }
      }
    }
  })

}

我接下来要做的是获取用户的响应，并为每个状态显示某些信息。我不知道有任何其他方法可以做到这一点，所以我检查了attending 和notAttending 两个列表，如果用户有响应，我会更改事件属性。

makeEvents(event) {
console.log(event)

event.goingText = "RSVP"
event.setGoing = 'rsvp'
event.setColor = "rsvp-color"

const attending = this.db.object(`attendingLookup/${this.uid}/${event.key}`).valueChanges()

this.attendingLookupSub = attending
  .subscribe(data => {
    console.log('attending', data)
    if (data) {
      event.goingText = "ATTENDING"
      event.setGoing = 'thumbs-up'
      event.setColor = 'attending-color'
    }
  })

const notAttending = this.db.object(`not_attendingLookup/${this.uid}/${event.key}`).valueChanges()

this.notAttendingLookupSub = notAttending
  .subscribe(data => {
    console.log('not attending', data)
    if (data) {
      event.goingText = "NOT ATTENDING"
      event.setGoing = 'thumbs-down'
      event.setColor = 'not-attending-color'
    }
  })

this.events.push(event)

}

*** 编辑

const eventsGuestsLookup = this.db.object(`eventsGuestsLookup/${this.uid}`).valueChanges()
eventsGuestsLookup.subscribe(keys => {
  of(keys).pipe(
    mergeMap(keys => {
      Object.keys(keys).map(k => {
        console.log(k)
      })
      return merge(Object.keys(keys).map(k => this.db.object(`events/${k}`)))
    })
  ).subscribe(data => console.log('data', data))
})

Answer 1

你想要实现的是扁平化你的 observables 集合。要实现它，您可以执行以下操作：

//Dummy eventKeys observable.
const obs1$ = new BehaviorSubject({key:1, action: 'lorem'});
const obs2$ = new BehaviorSubject({key:2, action: 'lorem'});
const obs3$ = new BehaviorSubject({key:3, action: 'lorem'});

const eventKeys = {
  obs1$,
  obs2$,
  obs3$
};
// Dummy eventsGuestsLookup observable.
of(eventKeys)
.pipe(
  //eventsGuestsLookup dispatch collection of obserbable, we want to flat it.
  mergeMap(ev => {
    // We merge all observables in new one.
    return merge(...Object.keys(ev).map(k => ev[k]));
  }),
).subscribe(console.log);

重要提示：ev[k] 是一个 Observable 对象。在您的情况下，您应该执行以下操作：

.map(k => this.db.object(`events/${k}`)) // will return observable.

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