Coordinator.swift

nextPresentable.rxFirstTimeVisible.subscribe(onSuccess: { [unowned self,
                                                           unowned nextPresentable,
                                                           unowned nextStepper] (_) in
    // we listen to the presentable's Stepper.
    // For each new Step value, we trigger a new navigation process
    // this is the core principle of the whole RxFlow mechanism
    // The process is paused each time the presentable is not currently displayed
    // for instance when another presentable is above it in the VCs hierarchy.
    nextStepper.steps
        .pausable(nextPresentable.rxVisible.startWith(true))
        .asDriver(onErrorJustReturn: NoStep())
        .drive(onNext: { [unowned self] (step) in
            // the nextPresentable's Stepper fires a new Step
            self.steps.onNext(step)
        }).disposed(by: nextPresentable.disposeBag)

}).disposed(by: self.disposeBag)