Refactoring Massive App Delegate using Command pattern. See blog post for more details: https://www.vadimbulavin.com/refactoring-massive-app-delegate

RefactoringAppDelegate-Command.swift

// MARK: - Builder

final class StartupCommandsBuilder {
    private var window: UIWindow!

    func setKeyWindow(_ window: UIWindow) -> StartupCommandsBuilder {
        self.window = window
        return self
    }

    func build() -> [Command] {
        return [
            InitializeThirdPartiesCommand(),
            InitialViewControllerCommand(keyWindow: window),
            InitializeAppearanceCommand(),
            RegisterToRemoteNotificationsCommand()
        ]
    }
}

// MARK: - App Delegate

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        StartupCommandsBuilder()
            .setKeyWindow(window!)
            .build()
            .forEach { $0.execute() }

        return true
    }
}