Two Rx Steam

TwoStream.swift

import RxSwift
import RxCocoa

func ignoreNil<A>(x: A?) -> Observable<A> {
  return x.map { Observable.just($0) } ?? Observable.empty()
}

var stream: BehaviorRelay<String?> = BehaviorRelay(value: nil)

var streamA: BehaviorRelay<String?> = BehaviorRelay(value: nil)
var streamB: BehaviorRelay<String?> = BehaviorRelay(value: nil)
var streamC: BehaviorRelay<String?> = BehaviorRelay(value: nil)
let bag = DisposeBag()

stream
    .flatMap(ignoreNil)
    .distinctUntilChanged().subscribe(onNext: { stream in
        print(stream)
    }).disposed(by: bag)

stream
    .flatMap(ignoreNil)
    .distinctUntilChanged()
    .withLatestFrom(
        BehaviorRelay.combineLatest(
            streamA
                .flatMap(ignoreNil)
                .distinctUntilChanged(),
            streamB
                .flatMap(ignoreNil)
                .distinctUntilChanged(),
            streamC
                .flatMap(ignoreNil)
                .distinctUntilChanged()
        )
    )
    .subscribe(onNext: { A, B, C in
        print(A)
        print(B)
        print(C)
    }).disposed(by: bag)

streamA.accept("A")
streamB.accept("B")
streamC.accept("C")
stream.accept("Trigger")


/* result
Trigger
A
B
C

*/