Managing subscriptions based on async event - asynchronous

Question

Im looking a way to simplify this and avoid managing subscriptions inside my pipe.
The general idea abought my code:
this.start$ubject // waiting for users call to start
.pipe(
mergeMap(() => from(this.thirdPartyService.start())), // now i need to wait for smth to start
tap(() => {
// only after thirdPartyService started i can subscribe because prior to that they are undefined
this.subscriptions.push(
this.thirdPartyService.alfa$.subscribe(this.first$ubject),
this.thirdPartyService.beta$.subscribe(this.second$ubject),
);
}),
);
Is there any way to deal with that? Something like takeWhile but for subscription?

Answer 1

try like that:
// waits for start$ubject, then waits for thirdPartyService, then starts.
this.subscriptions.push(
this.start$ubject.pipe(
switchMap(() => from(this.thirdPartyService.start())), // waiting start
switchMap(() => merge( // listening on both of the streams
this.thirdPartyService.alfa$.pipe(
tap(this.first$ubject),
),
this.thirdPartyService.beta$.pipe(
tap(this.second$ubject),
),
)),
).subscribe(),
);
// waits for start$ubject or for thirdPartyService, then starts.
this.subscriptions.push(
merge(this.start$ubject, from(this.thirdPartyService.start()).pipe(
switchMap(() => merge( // listening on both of the streams
this.thirdPartyService.alfa$.pipe(
tap(this.first$ubject),
),
this.thirdPartyService.beta$.pipe(
tap(this.second$ubject),
),
)),
).subscribe(),
);