Push Assign UNUserNotificationCenter delegate

AppDelegate.swift

import UIKit
import UserNotifications

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        //Assign the push delegate before didFinishLaunchingWithOptions completes
        UNUserNotificationCenter.current().delegate = PushManager.sharedInstance

        PushManager.sharedInstance.registerForPushNotifications()
        return true
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        PushManager.sharedInstance.didRegisterForRemoteNotifications(deviceToken: deviceToken)
    }

    func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
        print("didFailToRegisterForRemoteNotificationsWithError: \(error)")
    }

}