UIKit + Coordinator

Coordinator.swift

import Foundation
import UIKit

protocol Coordinator {
    var viewController: UIViewController? {get}
    var navigationController: UINavigationController? {get}
    
    func start()
}

extension Coordinator {
    var viewController: UIViewController? {nil}
    var navigationController: UINavigationController? {nil}
}

MainCoordinator.swift

import Foundation
import UIKit

class MainCoordinator: Coordinator {
    var navigationController: UINavigationController?
    
    init(navigationController: UINavigationController? = nil) {
        self.navigationController = navigationController
    }
    
    func start() {
        let vc = ViewController()
        navigationController?.pushViewController(vc, animated: true)
    }
    
    func showDetail(item: Model) {
        let vc = DetailViewController(item: item)
        navigationController?.pushViewController(vc, animated: true)
    }
    
}

SceneDeletate.swift

import UIKit

class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?
    var mainCoordinator: MainCoordinator?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        
        guard let windowScene = (scene as? UIWindowScene) else { return }
        window = UIWindow(windowScene: windowScene)
       
        let navigation = UINavigationController()
        mainCoordinator = MainCoordinator(navigationController: navigation)
        
        window?.rootViewController = navigation
        window?.makeKeyAndVisible()
        
        mainCoordinator?.start()
    }
}