MVVM-C-iOS

This project is to implement the MVVM-C (Model-View-ViewModel-Coordinator) architecutre pattern in an iOS app. The Coordinator pattern was introduced by Soroush Khanlou at the NSSpain conference in 2015. I use the following pieces to learn more about the Coordinator pattern:

• "Presenting Coordinators" by Soroush Khanlou
• "Navigation in Swift" by John Sundell

Architecture

Navigation

A coordinator owns a navigation controller to present view controllers, that has a delegate reference to the coordinator to call delegate methods for naviagations. Each coordinator use the start() function to present its view controller(s). A coordinator also owns an array of children coordinator to present another navigation flow managed by its child coordinator.

import UIKit

protocol Coordinator {
  var children: [Coordinator] { get set }
  init(navigationController: UINavigationController)
  func start()
}

class AppCoordinator: Coordinator {
  var children: [Coordinator]
  let navigationController: UINavigationController
  
  init(navigationController: UINavigationController) {
    self.navigationController = navigationController
  }
  
  func start() {
    let vc1 = ViewController1()
    vc1.navigationDelegate = self
    navigationController.pushViewController(vc1, animated: true)
  }
}

extension AppCoordinator: MainViewControllerNavigationDelegate {
  func navigateToViewController1() {
    navigationController.popToRootViewController(animated: true)
  }
  
  func navigateToViewController2() {
    let vc2 = ViewController2()
    vc2.navigationDelegate = self
    navigationController.pushViewController(vc2, animated: true)
  }
}

Presentation

Each view controller has a delegate reference to its coordinator to separate navigation logics, besides handling presentation with data binding through its view model.

import UIKit

protocol MainViewControllerNavigationDelegate: AnyObject {
  func navigateToViewController1()
  func navigateToViewController2()
  func navigateToLogin()
}

class ViewController1: UIViewController {
  weak var navigationDelegate: MainViewControllerNavigationDelegate?
  ...
  
  @objc
  func didTapShowVC2() {
    navigationDelegate?.navigateToViewController2()
  }
  
  @objc
  func didTapLogin() {
    navigationDelegate?.navigateToLogin()
  }
}

class ViewController2: UIViewController {
  weak var navigationDelegate: MainViewControllerNavigationDelegate?
  ...
  
  @objc
  func didTapShowVC1() {
    navigationDelegate?.navigateToViewController1()
  }
}

Business Logics

View models and other service, worker components handles business logics.

Say there is another login flow managed by LoginCoordinator. When a user taps the login button from ViewController1, it will trigger AppCoordinator to create LoginCoordinator and present LoginViewController. Afterwards, the user finish the login flow by calling the delgate method loginDidFinish, and it will trigger AppCoordinator to dismiss the login flow presentation and remove LoginCoordinator from its children coordinators.

extension AppCoordinator: MainViewControllerNavigationDelegate {
  func navigateToLogin() {
    let loginCoordinator = LoginCoordinator(navigationController: UINavigationController())
    loginCoordinator.delegate = self
    children.append(loginCoordinator)
    loginCoordinator.start()
  }
}

protocol LoginCoordinatorDelegate {
  func loginDidFinish()
}

extension AppCoordinator: LoginCoordinatorDelegate {
  func loginDidFinish() {
    navigationController.popViewController(animated: true)
    children.removeLast()
  }
}

class LoginCoordinator: Coordinator {
  var children: [Coordinator]
  weak var delegate: LoginCoordinatorDelegate?
  let navigationController: UINavigationController
  
  init(navigationController: UINavigationController) {
    self.navigationController = navigationController
  }
  
  func start() {
    let vc = LoginViewController()
    vc.navigationDelegate = self
    navigationController.pushViewController(vc, animated: true)
  }
}

extention LoginCoordinator: LoginViewControllerNavigationDelegate {
  func navigateToFacebookLogin() {
    ...
  }
  func navigateToMain() {
    delegate?.loginDidFinish()
  }
}

protocol LoginViewControllerNavigationDelegate: AnyObject {
  func navigateToFacebookLogin()
  func navigateToMain()
}

class LoginViewController: UIViewController {
  weak var navigationDelegate: LoginViewControllerNavigationDelegate?
  ...
  
  @objc
  func didTapLogin() {
    navigationDelegate?.navigateToFacebookLogin()
  }
  
  func didFinishLogin() {
    navigationDelegate?.navigateToMain()
  }
}