SceneCoordinator

SceneCoordinator.swift

import UIKit
import RxSwift
import RxCocoa

final class SceneCoordinator: SceneCoordinatorType {
    
    fileprivate var window: UIWindow
    var currentViewController: UIViewController
    
    required init(window: UIWindow) {
        self.window = window
        currentViewController = window.rootViewController!
    }
    
    static func actualViewController(for viewController: UIViewController) -> UIViewController {
        if let navigationController = viewController as? UINavigationController {
            return navigationController.viewControllers.first!
        } else {
            return viewController
        }
    }
    
    @discardableResult
    func transition(to scene: Scene, type: SceneTransitionType) -> Observable<Void> {
        let subject = PublishSubject<Void>()
        let viewController = scene.viewController()
        switch type {
        case .root:
            currentViewController = SceneCoordinator.actualViewController(for: viewController)
            window.rootViewController = viewController
            subject.onCompleted()
            
        case .push(let animated):
            guard let navigationController = currentViewController.navigationController else {
                fatalError("Can't push a view controller without a current navigation controller")
            }
            // one-off subscription to be notified when push complete
            _ = navigationController.rx.delegate
                .sentMessage(#selector(UINavigationControllerDelegate.navigationController(_:didShow:animated:)))
                .map { _ in }
                .bind(to: subject)
            navigationController.pushViewController(viewController, animated: animated)
            currentViewController = SceneCoordinator.actualViewController(for: viewController)
            
        case .modal(let animated):
            currentViewController.present(viewController, animated: animated) {
                subject.onCompleted()
            }
            currentViewController = SceneCoordinator.actualViewController(for: viewController)
            
        case .pushToVC(let stack, let animated):
            guard let navigationController = currentViewController.navigationController else {
                fatalError("Can't push a view controller without a current navigation controller")
            }
            
            var controllers = navigationController.viewControllers
            stack.forEach { controllers.append($0) }
            controllers.append(viewController)
            
            // one-off subscription to be notified when push complete
            _ = navigationController.rx.delegate
                .sentMessage(#selector(UINavigationControllerDelegate.navigationController(_:didShow:animated:)))
                .map { _ in }
                .bind(to: subject)
            navigationController.setViewControllers(controllers, animated: animated)
            currentViewController = SceneCoordinator.actualViewController(for: viewController)
            
        default:
            break
        }
        return subject.asObservable()
            .take(1)
            .ignoreElements()
    }
    
    @discardableResult
    func pop(animated: Bool) -> Observable<Void> {
        let subject = PublishSubject<Void>()
        if let presenter = currentViewController.presentingViewController {
            // dismiss a modal controller
            currentViewController.dismiss(animated: animated) {
                self.currentViewController = SceneCoordinator.actualViewController(for: presenter)
                subject.onCompleted()
            }
        } else if let navigationController = currentViewController.navigationController {
            // navigate up the stack
            // one-off subscription to be notified when pop complete
            _ = navigationController.rx.delegate
                .sentMessage(#selector(UINavigationControllerDelegate.navigationController(_:didShow:animated:)))
                .take(1) // To delete if already in return at bottom
                .map { _ in }
                .bind(to: subject)
            
            guard navigationController.popViewController(animated: animated) != nil else {
                fatalError("can't navigate back from \(currentViewController)")
            }
            currentViewController = SceneCoordinator.actualViewController(for: navigationController.viewControllers.last!)
        } else {
            fatalError("Not a modal, no navigation controller: can't navigate back from \(currentViewController)")
        }
        return subject.asObservable()
            .take(1)
            .ignoreElements()
    }
    
    @discardableResult
    func popToRoot(animated: Bool) -> Observable<Void> {
        
        let subject = PublishSubject<Void>()
        
        if let navigationController = currentViewController.navigationController {
            // navigate up the stack
            // one-off subscription to be notified when pop complete
            _ = navigationController.rx.delegate
                .sentMessage(#selector(UINavigationControllerDelegate.navigationController(_:didShow:animated:)))
                .take(1) // To delete if already in return at bottom
                .map { _ in }
                .bind(to: subject)
            
            guard navigationController.popToRootViewController(animated: animated) != nil else {
                fatalError("can't navigate back to root VC from \(currentViewController)")
            }
            currentViewController = SceneCoordinator.actualViewController(for: navigationController.viewControllers.first!)
        }
        
        return subject.asObservable()
            .take(1)
            .ignoreElements()
    }
    
    @discardableResult
    func popToVC(_ viewController: UIViewController, animated: Bool) -> Observable<Void> {
        
        let subject = PublishSubject<Void>()
        
        if let navigationController = currentViewController.navigationController {
            // navigate up the stack
            // one-off subscription to be notified when pop complete
            _ = navigationController.rx.delegate
                .sentMessage(#selector(UINavigationControllerDelegate.navigationController(_:didShow:animated:)))
                .take(1) // To delete if already in return at bottom
                .map { _ in }
                .bind(to: subject)
            
            guard navigationController.popToViewController(viewController, animated: animated) != nil else {
                fatalError("can't navigate back to VC from \(currentViewController)")
            }
            currentViewController = SceneCoordinator.actualViewController(for: navigationController.viewControllers.last!)
        }
        return subject.asObservable()
            .take(1)
            .ignoreElements()
    }
}

I changed the result of the method (which was Observable) to Completable.

By the way, If you set function return type from Observable<Void> to Completable, you will see Xcode compiler error.

Compiler error

Cannot convert return expression of type 'Observable<Never>' to return type 'Completable' (aka 'PrimitiveSequence<CompletableTrait, Never>')

Solution

return subject.asObservable()
            .take(1)
            .ignoreElements()
            .asCompletable() // Add This Operator.