Optimal Push Notification Pattern

AppDelegate.swift

class AppDelegate: UIResponder, UIApplicationDelegate {
    private var currentUserNotificationTypes: UIUserNotificationType = .None

    private func processUpdatedUserNotificationSettings(application: UIApplication, currentUserNotificationSettings notificationSettings: UIUserNotificationSettings?) {
        let newUserNotificationTypes: UIUserNotificationType = notificationSettings?.types ?? .None
        
        // only performs actions if the current value has a delta with the new value
        if currentUserNotificationTypes.contains(.Alert) != newUserNotificationTypes.contains(.Alert) {
            self.currentUserNotificationTypes = newUserNotificationTypes
            
            if newUserNotificationTypes.contains(.Alert) {
                application.registerForRemoteNotifications()
            } else {
                self.alertDisplayingServices.forEach({ $0.applicationLostAlertNotificationsCapability() })
            }
        }
    }
    
    // MARK: - UIApplicationDelegate
    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        // updates cached permission settings + gets a fresh APNS token, if needed
        self.processUpdatedUserNotificationSettings(application, currentUserNotificationSettings: application.currentUserNotificationSettings())
        
        ...
    }
    
    func applicationWillEnterForeground(application: UIApplication) {
        self.processUpdatedUserNotificationSettings(application, currentUserNotificationSettings: application.currentUserNotificationSettings())
    }
    
    func application(application: UIApplication, didRegisterUserNotificationSettings notificationSettings: UIUserNotificationSettings) {
        self.processUpdatedUserNotificationSettings(application, currentUserNotificationSettings: notificationSettings)
    }
    
    func application(application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: NSData) {
        if self.currentUserNotificationTypes.contains(.Alert) {
            self.alertDisplayingServices.forEach({ $0.applicationGainedAlertNotificationsCapability(remoteNotificationDeviceToken: deviceToken) })
        }
    }
    
    func application(application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: NSError) {
        if self.currentUserNotificationTypes.contains(.Alert) {
            self.alertDisplayingServices.forEach({ $0.applicationLostAlertNotificationsCapability() })
        }
    }
}

To use this, just issue a UIApplication.sharedApplication().registerUserNotificationSettings: call within your application. This will trigger a request for the appropriate permissions from the user, and the rest of the pattern will take over from there (ending in the appropriate notifications being sent to self.alertDisplayingServices).