Swift, iOS: How to get Polymorphic and Decouple Coordinator from concrete type

Question

I have these protocols:

protocol Coordinator {
    var rootViewController: UIViewController { get set }
    func start()
}

protocol UIViewControllerFactory {
    func mainViewController() -> UIViewController
}

And I created a MainCoordinator that conforms to this protocol and I pass a factory that allows me to decouple the coordinator from creating and capturing a concrete type so it can be polymorphic and can be used with more implementations of UIViewController either as rootViewControllers and mainMenuViewController as shown below:

class MainCoordinator: Coordinator {
    var rootViewController: UIViewController
    let factory: UIViewControllerFactory 
    
    init(rootViewController: UIViewController, factory: UIViewControllerFactory) {
        self.rootViewController = rootViewController
    }
    
    start() {
        guard let mainVC = factory.mainViewController() as? MainViewController, let rootViewController = rootViewController as? UINavigationViewController  else { return }
        
        mainVC.delegate = self
        rootViewController.push(mainVC, animated: true)
    }

As you can see, although I've created the coordinator to accept any subclass of UIViewController it has been coupled in the start function to the concrete implementation of UIViewController: MainViewController.

How can I decouple it from MainViewController and have it more polymorphic?

Answer 1

You can pass coordinator as a parameter type in factory function and set delegate directly in factory function while creating controller instance. That way you wouldn’t have to expose controller type explicitly out of factory classes.

I came up with below approach.

protocol Coordinator {
    var rootViewController: UIViewController { get set }
    func start()
}

protocol UIViewControllerFactory {
    func getViewController(delegateType:CoordinatoreTypes,delegateObject:Coordinator) -> UIViewController?
}

class MainCoordinator: Coordinator {
    var rootViewController: UIViewController
    let factory: UIViewControllerFactory
    
    init(rootViewController: UIViewController, factory: UIViewControllerFactory) {
        self.rootViewController = rootViewController
        self.factory = factory
    }
    
    func start() {
        guard let controller = factory.getViewController(delegateType: .MainCoordinator, delegateObject: self),let rootViewController = rootViewController as? UINavigationViewController else {
            return
        }
        rootViewController.push(mainVC, animated: true)
    }
}

extension MainCoordinator:DelegateCaller{
    func printHello() {
        print("helloo")
    }
}

enum CoordinatoreTypes{
    case MainCoordinator
    case none
}

class Factory:UIViewControllerFactory{
    func getViewController(delegateType:CoordinatoreTypes,delegateObject:Coordinator) -> UIViewController?{
        switch delegateType{
        case .MainCoordinator:
            let controller = MainViewController()
            controller.delegate = delegateObject as? MainCoordinator
            return controller
        case .none:
            break
        }
        return nil
    }
}

class MainViewController:UIViewController{
    weak var delegate:DelegateCaller?
}

protocol DelegateCaller:AnyObject{
    func printHello()
}