Coordinators and deep linking

How we handle navigation inside the mobile bank at DNB

Transcript

1. Coordinators and deep linking
   How we handle navigation inside the mobile bank
   

   View Slide

2. Big app with lots of screens
   

   View Slide

3. • Coordinators are responsible for the presentation flow between view
   controllers.
   • View controllers have no knowledge about the context they are being used.
   The coordinator pattern
   protocol Coordinator: class {
   var childCoordinators: [Coordinator] { get set }
   }
   

   View Slide

4. Tree of coordinators
   

   View Slide

5. Reusing sub-flows
   

   View Slide

6. class AppCoordinator: Coordinator {
   func open(deepLink: DeepLink, animated: Bool) {
   if authService.isAuthenticated {
   tabBarCoordinator.open(deepLink: deepLink, animated: animated)
   } else {
   showAuthCoordinator()
   }
   }
   }
   

   View Slide

7. Deep linking
   

   View Slide

8. enum DeepLink {
   case pay
   case transfer
   case pendingPayments
   case accountDetail(id: String)
   }
   protocol Coordinator: class {
   var childCoordinators: [Coordinator] { get set }
   func open(deepLink: DeepLink, animated: Bool)
   }
   

   View Slide

9. Pay
   

   View Slide

10. class AppCoordinator: Coordinator {
    ...
    func open(deepLink: DeepLink, animated: Bool) {
    if authService.isAuthenticated {
    tabBarCoordinator.open(deepLink: deepLink, animated: animated)
    } else {
    showAuthCoordinator()
    }
    }
    }
    

    View Slide

11. Problem #1
    • Each new deep link requires you to update the entire tree of coordinators
    

    View Slide

12. View Slide

13. Settings Pay
    

    View Slide

14. Problem #2
    • Need to manually remove references to coordinators when navigating
    backwards in a navigation controller
    

    View Slide

15. Need to remember to remove any
    references to this coordinator
    

    View Slide

16. extension Coordinator: UINavigationControllerDelegate {
    func navigationController(
    navigationController: UINavigationController,
    didShowViewController viewController: UIViewController,
    animated: Bool
    ) {
    guard
    let fromViewController = navigationController.transitionCoordinator?.viewController(forKey: .from),
    !navigationController.viewControllers.contains(fromViewController) else {
    return
    }
    if fromViewController is HomeViewController {
    homeCoordinator = nil
    }
    }
    }
    Back button problem
    

    View Slide

17. Revised version
    

    View Slide

18. Automatically deallocate coordinators
    open class NavigationCoordinator: NSObject, Coordinator, UINavigationControllerDelegate {
    weak var parentCoordinator: NavigationCoordinator?
    var rootViewController: UIViewController
    var navigationController: UINavigationController
    var childCoordinators: [Coordinator]
    var childViewControllers: [WeakRef]
    init(rootViewController: UIViewController, navigationController: UINavigationController) {
    self.childCoordinators = []
    self.childViewControllers = []
    self.rootViewController = rootViewController
    self.navigationController = navigationController
    super.init()
    }
    ...
    public func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
    guard let toViewController = navigationController.transitionCoordinator?.viewController(forKey: .to) else { return }
    removeIfNeeded(coordinator: self, toViewController: toViewController)
    }
    private func contains(coordinator: NavigationCoordinator, viewController: UIViewController) -> Bool {
    return coordinator.childViewControllers.contains(where: { $0.value === viewController })
    }
    func removeIfNeeded(coordinator: NavigationCoordinator, toViewController: UIViewController) {
    if contains(coordinator: coordinator, viewController: toViewController) {
    return
    }
    else if let parentCoordinator = coordinator.parentCoordinator {
    parentCoordinator.remove(coordinator: coordinator)
    parentCoordinator.set(delegate: parentCoordinator)
    removeIfNeededcoordinator: parentCoordinator, toViewController: toViewController)
    

    View Slide

19. Example
    final class AccountDetailCoordinator: NavigationCoordinator {
    }
    func select() {
    let viewController = AccountConditionsViewController()
    viewController.coordinator = self
    push(viewController: viewController, animated: true)
    }
    func selectConditions() {
    push(coordinator: AccountDetailCoordinator(navigationController))
    }
    

    View Slide

20. Problem #3
    • View controller could not use UINavigationControllerDelegate
    • Basically reimplementing stuff we get for free in UIKit
    

    View Slide

21. Back to basics
    • Just use view controllers directly?
    • Can get the separation using parent/child view controllers
    • Hard to reuse sub-flows in navigation controllers
    

    View Slide

22. Flip it around
    

    View Slide

23. What about deep linking?
    • We no longer have a tree of coordinators
    • Traverse the view controller hierarchy instead
    • Need to associate a given view controller with something
    

    View Slide

24. struct DeepLink {
    let destination: Destination
    let path: [Destination]
    }
    enum Destination {
    case home
    case payments
    case spending
    case profile
    case pay
    case transfer
    case pendingPayments
    case accountDetail(id: String)
    }
    

    View Slide

25. DeepLinkable
    protocol DeepLinkable {
    var destination: Destination { get }
    var coordinator: Coordinator { get }
    }
    final class AccountDetailViewController: UIViewController, DeepLinkable {
    let destination: Destination
    let coordinator: HomeCoordinator
    init(id: String, coordinator: HomeCoordinator) {
    self.coordinator = coordinator
    self.destination = .accountDetail(id: id)
    super.init(nibName: nil, bundle: nil)
    }
    }
    

    View Slide

26. Settings Pay
    

    View Slide

27. Demo
    

    View Slide

28. Tips for deep linking
    • Usually no need for coordinators
    • Each view controller should fetch data in isolation
    init(model: Account)
    init(id: String)
    

    View Slide

29. View Slide