Coordinator and why it's the best reason to refactor your project

Talk by Мария Голубева

Поговорим об архитектурном паттерне Координатор, о его плюсах и минусах, когда стоит его имплементировать, а когда его использование будет оверинжинирингом, рассмотрим несколько вариантов его реализации на реальном проекте.

This talk was made for CocoaFriday #2 ( https://cocoaheads.org.ua/cocoafriday/2 ) which took place Apr 5, 2019.

Video: https://youtu.be/ewBChYlQtaQ

Transcript

1. COORDINATOR
   AND WHY IT’S THE BEST REASON TO
   REFACTOR YOUR PROJECT
   Maria Holubieva, Software Engineer at Synergetica
   

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2. A long time ago in a galaxy far,
   far away…
   

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3. A long time ago in a galaxy far,
   far away…
   CLEAN
   ARCHITECTURE
   +
   MVP
   

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4. A long time ago in a galaxy far,
   far away…
   CLEAN
   ARCHITECTURE
   +
   MVP
   SOLID
   PRINCIPLES
   +
   TWO SENIOR
   DEVS
   

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5. A long time ago in a galaxy far,
   far away…
   CLEAN
   ARCHITECTURE
   +
   MVP
   SOLID
   PRINCIPLES
   +
   TWO SENIOR
   DEVS
   PROFIT
   

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6. CLEAN
   ARCHITECTURE
   +
   MVP
   SOLID
   PRINCIPLES
   +
   TWO SENIOR
   DEVS
   TYPICAL
   PROJECT*
   * with it’s own problems
   

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7. WHAT DID WE HAVE AT THE
   MIDDLE OF THE FIRST YEAR?
   

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8. WHAT DID WE HAVE AT THE MIDDLE OF THE FIRST YEAR?
   - NAVIGATION THROUGH ROUTER
   PRESENTER
   ROUTER
   Navigation
   between
   modules
   VIEW CONTROLLER
   data to display
   user actions
   MODEL
   request data
   

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9. WHAT DID WE HAVE AT THE MIDDLE OF THE FIRST YEAR?
   - NAVIGATION THROUGH ROUTER
   - SIMPLE ONE DIRECTIONAL APP FLOWS
   present push push
   dismiss
   

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10. WHAT DID WE HAVE AT THE MIDDLE OF THE FIRST YEAR?
    - NAVIGATION THROUGH ROUTER
    - SIMPLE ONE DIRECTIONAL APP FLOWS
    - PASSING DATA BETWEEN TWO NEIGHBOR
    MODULES
    LOGIN MODULE MAIN SCREEN
    MODULE
    current consumer
    

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11. AND IN 2 YEARS…
    

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12. AND IN 2 YEARS…
    COMPLEX NAVIGATION WITH MODULES REUSING IN
    THE DIFFERENT FLOWS
    SEARCH FOR
    SUBCATEGORY
    SEARCH FOR
    A TRAINER
    CHOOSE
    FITNESS
    ACTIVITY
    TYPE
    TRAINER
    PROFILE
    CREATE
    APPOINTMENT
    SEARCH FOR
    SUBCATEGORY
    TRAINER
    PROFILE
    for gym
    activity
    type
    for group
    activity type
    for any
    currently available
    activity type
    

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13. AND IN 2 YEARS…
    PRESENTER MUST KNOW THE FLOW TYPE
    SEARCH FOR
    GYM ACTIVITY
    SEARCH FOR
    GROUP ACTIVITY
    

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14. AND IN 2 YEARS…
    DIFFERENT DATA PASSING BETWEEN MODULES DEPENDS ON THE FLOW TYPE
    CHOOSE
    FITNESS
    ACTIVITY
    TYPE
    SEARCH FOR
    SUBCATEGORY
    TRAINER
    PROFILE
    flow type
    SEARCH FOR
    A TRAINER
    Gym activity
    • flow type
    • subcategory ID
    Group activity
    • flow type
    • trainer ID
    • flow type
    • trainer ID
    

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15. AND IN 2 YEARS…
    NEED TO STORE UNUSED DATA, REQUIRED FOR THE NEXT MODULES
    CHOOSE
    APPOINTMENT
    DATE & TIME
    CHOOSE
    FITNESS
    CLUB
    CHOOSE
    TRAINER
    APPOINTMENT
    SUMMARY
    • trainerID
    • trainerID
    • fintessClubID
    • trainerID
    • fintessClubID
    • choosedDate
    

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16. CONCLUSIONS
    OUR PROJECT PROBLEMS
    ▸ it’s hard to reuse Modules
    ▸ every Module knows about other Modules
    ▸ it’s hard to change Flows
    ▸ it’s hard to test Flows
    

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17. COORDINATOR
    AND WE FOUNT A GOOD SOLUTION
    

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18. WHAT IS COORDINATOR?
    COORDINATOR IS RESPONSIBLE FOR THE APPLICATION’S FLOW
    CHOOSE
    FITNESS
    ACTIVITY
    TYPE
    START GYM
    ACTIVITY
    COORDINATOR
    START GROUP
    ACTIVITY
    COORDINATOR
    START ANY
    ACTIVITY
    COORDINATOR
    

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19. WHAT IS COORDINATOR?
    THE COORDINATOR KNOWS NOTHING OF ITS PARENT
    COORDINATOR, BUT IT CAN ADD CHILD COORDINATORS
    Fitness activity coordinator
    SEARCH FOR
    SUBCATEGORY
    SEARCH FOR
    A TRAINER
    TRAINER
    PROFILE
    START
    add child
    create appointment
    coordinator
    

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20. IT IS CODING
    TIME…
    

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21. ▸ Create your own app starting point
    

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22. protocol Coordinator: class {
    func start()
    }
    ▸ declare Coordinator protocol
    

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23. class ApplicationCoordinator: Coordinator {
    private let window: UIWindow
    private let navigationController: UINavigationController
    init(window: UIWindow) {
    self.window = window
    navigationController = UINavigationController()
    }
    func start() {
    window.rootViewController = navigationController
    window.makeKeyAndVisible()
    showChooseActivityTypeScreen()
    }
    private func showChooseActivityTypeScreen() {
    let viewController = ChooseActivityTypeViewController()
    rootViewController.pushViewController(viewController,
    animated: false)
    }
    }
    ▸ implement ApplicationCoordinator class
    

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24. @UIApplicationMain
    class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    private var applicationCoordinator: ApplicationCoordinator?
    func application(_ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions:
    [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    let window = UIWindow(frame: UIScreen.main.bounds)
    let applicationCoordinator = ApplicationCoordinator(window: window)
    self.window = window
    self.applicationCoordinator = applicationCoordinator
    applicationCoordinator.start()
    return true
    }
    }
    ▸ start ApplicationCoordinator
    

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25. LET’S ADD
    MORE…
    

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26. protocol Coordinator: class {
    var onFinish: (() -> Void)? { get set }
    func start()
    }
    class BaseCoordinator {
    var childCoordinators: [Coordinator] = []
    func addDependency(_ coordinator: Coordinator) {
    for element in childCoordinators {
    if element === coordinator { return }
    }
    childCoordinators.append(coordinator)
    }
    func removeDependency(_ coordinator: Coordinator?) {
    guard childCoordinators.isEmpty == false,
    let coordinator = coordinator else { return }
    for (index, element) in childCoordinators.enumerated() {
    if element === coordinator {
    childCoordinators.remove(at: index)
    break
    }
    }
    }
    }
    ▸ add ability to build Coordinators hierarchy
    

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27. class ApplicationCoordinator: BaseCoordinator, Coordinator {
    private let window: UIWindow
    private let navigationController: UINavigationController
    init(window: UIWindow) {
    self.window = window
    navigationController = UINavigationController()
    }
    func start() {
    window.rootViewController = navigationController
    window.makeKeyAndVisible()
    startChooseActivityFlow()
    }
    private func startChooseActivityFlow() {
    let chooseActivityCoordinator = ChooseActivityTypeCoordinator(with:
    navigationController)
    chooseActivityCoordinator.onFinish = {
    [weak self, weak weakCoordinator = chooseActivityCoordinator] in
    self?.removeDependency(weakCoordinator)
    }
    addDependency(chooseActivityCoordinator)
    chooseActivityCoordinator.start()
    }
    }
    ▸ change ApplicationCoordinator
    

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28. enum ActivityType {
    case fitness
    case group
    case any
    }
    class ChooseActivityTypeViewController: UIViewController {
    //...
    var onActivityTypeSelected: ((_ type: ActivityType) -> Void)?
    //...
    }
    ▸ add callback to ChooseActivityTypeViewController
    

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29. class ChooseActivityTypeCoordinator: BaseCoordinator, Coordinator {
    var onFinish: (() -> Void)?
    private unowned let navigationController: UINavigationController
    init(with navigationController: UINavigationController) {
    self.navigationController = navigationController
    }
    func start() {
    showChooseActivityTypeScreen()
    }
    private func showChooseActivityTypeScreen() {
    let vc = ChooseActivityTypeViewController()
    vc.onActivityTypeSelected = { [weak self] (activityType: ActivityType) in
    switch activityType {
    case .fitness: self?.startFitnessActivityFlow()
    case .group: self?.startGroupActivityFlow()
    case .any: self?.startAnyActivityFlow()
    }
    }
    navigationController.pushViewController(vc, animated: false)
    }
    //...
    }
    ▸ create ChooseActivityTypeCoordinator
    

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30. //...
    private func startFitnessActivityFlow() {
    let fitnessCoordinator = FitnessActivityCoordinator(with: navigationController,
    appointmentsManager: appointmentsManager)
    fitnessCoordinator.onFinish = {
    [weak self, weak weakCoordinator = fitnessCoordinator] in
    self?.removeDependency(weakCoordinator)
    self?.navigationController.popToRootViewController(animated: true)
    }
    addDependency(fitnessCoordinator)
    fitnessCoordinator.start()
    }
    //...
    ▸ add in ChooseActivityTypeCoordinator
    

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31. MY EXAMPLE
    FULL PROJECT
    ▸ https://github.com/miserya/CoordinatorExample
    

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32. MORE COMPLICATED COORDINATOR CONFIGURATIONS
    YOUR
    COORDINATOR
    COORDINATORS
    FACTORY
    ROUTER
    INSTRUCTOR
    STATE
    STORAGE
    ask for the next
    module to present
    save data
    ask to present
    next module
    the chosen way
    ask to create
    a coordinator
    

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33. IS IT A PERFECT SOLUTION?
    COORDINATOR
    

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34. ACTUALLY NO
    CONS
    ▸ you need to write more code;
    ▸ it’s not a solution for a small projects;
    ▸ you need to observe NavigationController pop action on
    swipe or default Back button tap;
    

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35. BUT!
    PROS
    ▸ Coordinators keep the project straightforward and the
    Modules independent;
    ▸ simple Modules reusing;
    ▸ with Coordinators it’s easier to implement new features/
    flows/navigations;
    ▸ app Flows become easier to test;
    ▸ initial Project’s architecture does not matter;
    

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36. THANK YOU!
    USEFUL LINKS
    ▸ https://www.raywenderlich.com/158-coordinator-tutorial-
    for-ios-getting-started
    ▸ https://medium.com/blacklane-engineering/coordinators-
    essential-tutorial-part-i-376c836e9ba7
    ▸ https://medium.com/blacklane-engineering/coordinators-
    essential-tutorial-part-ii-b5ab3eb4a74
    

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