Easily request permissions in iOS 9 and iOS 10

NotificationPermissionController.swift

import UIKit
import UserNotifications
import PropellerPromise

struct NotificationPermissionController {
    
    static var permissionsEnabled: Bool {
        guard let settings = UIApplication.shared.currentUserNotificationSettings else {
            return false
        }
        return settings.types.contains([.badge, .alert])
    }
    
    static func requestPermission() -> Promise<Bool> {
        let promise = Promise<Bool>()
        
        if #available(iOS 10.0, *) {
            UNUserNotificationCenter
                .current()
                .requestAuthorization(options: [.badge, .alert]) { success, error in
                    
                if let error = error {
                    promise.reject(error)
                    return
                }
                
                promise.fulfill(success)
                    
                if success {
                    registerForRemoteNotifications()
                }
            }
        } else {
            let settings = UIUserNotificationSettings(types: [.alert, .badge], categories: nil)
            UIApplication.shared.registerUserNotificationSettings(settings)
            NotificationCenter
                .default
                .addObserver(forName: .RemoteNotificationsRegistered,
                             object: nil,
                             queue: nil) { notification in
                                
                guard let success = notification.object as? Bool else { return }
                promise.fulfill(success)
                                
                if success {
                    registerForRemoteNotifications()
                }
            }
        }
        
        return promise
    }
    
    static func registerForRemoteNotifications() {
        UIApplication.shared.registerForRemoteNotifications()
    }
}

extension NSNotification.Name {
    
    static let RemoteNotificationsRegistered = NSNotification.Name(rawValue: "RemoteNotificationsRegistered")
}

extension AppDelegate {
    
    func application(_ application: UIApplication, didRegister notificationSettings: UIUserNotificationSettings) {
        guard let settings = application.currentUserNotificationSettings else { return }
        let success = settings.types.contains([.badge, .alert])
        
        NotificationCenter
            .default
            .post(name: .RemoteNotificationsRegistered,
                  object: success)
    }
    
    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        let token = deviceToken.apnsTokenString()
        // TODO:- Send token to server
    }
}

//MARK: - APNS Token extension -
private extension Data {
    
    func apnsTokenString() -> String {
        return map { String(format: "%02.2hhx", arguments: [$0]) }.joined()
    }
}