what triggered combineLatest?

Question

I have a few observables. And I need to know which one triggered the subscribe.

Observable.combineLatest(
      this.tournamentsService.getUpcoming(),
      this.favoriteService.getFavoriteTournaments(),
      this.teamsService.getTeamRanking(),
(tournament, favorite, team) => {
//what triggered combinelatest to run?
}).subscribe()

Answer 1

A quite clean and "rx"-way of achieving this is by using the timestamp operator http://reactivex.io/documentation/operators/timestamp.html

Example code

sourceObservable
  .pipe(
    timestamp(),  // wraps the source items in object with timestamp of emit
    combineLatest( otherObservable.pipe( timestamp() ), function( source, other ) {

      if( source.timestamp > other.timestamp ) {

        // source emitted and triggered combineLatest
        return source.value;
      }
      else {

        // other emitted and triggered combineLatest
        return other.value;
      }

    } ),
  )

If more than two observables are involved in the combineLatest() sorting them by timestamp would enable to detect which one triggered the combineLatest().