class ViewController: UIViewController { let disposeBag: DisposeBag = DisposeBag() @IBAction func onButton() { requestA().flatMap({ (responseA) -> Observable<Void> in requestB().map({ (responseB) -> Void in if responseA.isHoge, responseB.str == "xxx" { accept(responseA, responseB) } return () }) }).disposed(by: disposeBag) } }