Rxjs 将多个可观察对象组合成单个 boolean 可观察对象

Question

I am trying to Combine multiple observables to a single boolean observable.

Currently I'm using scan and it's running using the previously emitted value for the accumulator when I need it to use true every time. I'm not sure how to achieve this.

    this.partnershipFundInvalid$ = merge(
      this.partnershipFundId$.pipe(map(id => id === null)),
      this.partnershipsFileUploader.dataImportState$.pipe(map(state => state.file !== null)),
    ).pipe(
      scan((acc, val) => {
        return acc && val === true;
      }, true),
    );

Answer 1

Scan, but ignore the accumulated value

    this.partnershipFundInvalid$ = merge(
      this.partnershipFundId$.pipe(map(id => id === null)),
      this.partnershipsFileUploader.dataImportState$.pipe(map(state => state.file !== null)),
    ).pipe(
      scan((acc, val) => {
        return true && val === true; // Replaced acc with "true"
      }, true),
    );

That's semantically the same as map

    this.partnershipFundInvalid$ = merge(
      this.partnershipFundId$.pipe(map(id => id === null)),
      this.partnershipsFileUploader.dataImportState$.pipe(map(state => state.file !== null)),
    ).pipe(
      map(val => {
        return true && val === true;
      }),
    );

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map doesn't emit until all the streams are closed

That's not how map works, it doesn't deal with error or completion emissions.

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I would suggest updating your question to include what you're trying to accomplish as 'I am trying to "reduce" a Boolean' is ambiguous. There are many ways to "reduce" a Boolean

Answer 2

A friend suggested this, i was completely over thinking it.

this.partnershipFundInvalid$ = combineLatest(
  this.partnershipFundId$,
  this.partnershipsFileUploader.dataImportState$,
).pipe(
  map(([fundId, partnershipsFile]) => {
    return fundId == null && partnershipsFile.file !== null;
  }),
);