CODEWITHSUNDEEP
angularrxjs
Volodymyr Samoilenko
Volodymyr Samoilenko

Reputation: 358

Tap after switch map called only once

I have an issue with a switch map behavior.

I have selected spreadsheets ids, for each id I have a corresponding instance of UI component, I want to make a visual change at the beginning, then to do few google spreadsheet API calls and then make a visual change at the end. One note, that gapi client works outside of ngZone, to get it works correctly I'm using ngZone.zone.run.

const ids = [1,2]

function processSelectedIds(ids) {
  from(ids)
    .pipe(
      switchMap(id => processId(id)),
    )
    .subscribe({
      next: value => {
        console.log('subscribe next')
        this._state.ids = [] // clean selected ids
        this.stateSubject.next([...this._state.data]) // trigger ui update
      },
    })
}

function processId(id) {
  return of(id).pipe(
    tap(_ => {
     this.updateUI(id, STATE.start) // mutate state
     this.stateSubject.next([...this._state.sheets]) // trigger ui update
     console.log('before', id)
    }),
    switchMap(() => {
      console.log('switchMap', id)
      return getSpreadsheet(id)
    }),
    tap(_ => {
      console.log('after', id)
      this.updateUI(id, STATE.end) // mutate state
        this.zone.run(() => { // because getSpreadsheet runs outside of NgZone
          this.stateSubject.next([...this._state.sheets]) // trigger ui update
        })
      }),
    )
}

getSpreadsheet(id) {
 return forkJoin({
   response1: apiCall1(id),
   response2: apiCall2(id),
 }).pipe(
      map(response => {
        return parseResponse(response)
      }),
    )
}

My issue that second tap inside processId doesn't trigger. This is how looks my output:

before, 1
switchMap, 1

before, 2
switchMap, 2
after, 2

subscribe next

I cannot figure out what is wrong here, I would appreciate any help on how to make it works. Thanks in advance for your help

Upvotes: 1

Views: 901

Answers (1)

martin
martin

Reputation: 96909

It looks like the source Observable from(ids) emits too fast and switchMap() will unsubscribe before getSpreadsheet(id) can emit.

So maybe you are looking for concatMap() or mergeMap() instead.

Upvotes: 1

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