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

RefactoringAppDelegate-Composite.swift

typealias AppDelegateType = UIResponder & UIApplicationDelegate

class CompositeAppDelegate: AppDelegateType {
    private let appDelegates: [AppDelegateType]

    init(appDelegates: [AppDelegateType]) {
        self.appDelegates = appDelegates
    }

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        appDelegates.forEach { _ = $0.application?(application, didFinishLaunchingWithOptions: launchOptions) }
        return true
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        appDelegates.forEach { _ = $0.application?(application, didRegisterForRemoteNotificationsWithDeviceToken: deviceToken) }
    }
}