Why is my iOS device not registering and getPushToken() returns null when I use Pushwoosh with another push provider like Firebase?

When the Pushwoosh SDK shares an app with another push provider (Firebase, for example), both try to own UNUserNotificationCenterDelegate. Whichever one is assigned last wins, and Pushwoosh can never finish device registration — so the push token stays null and test pushes never arrive.

The fix is to register your other provider's delegate with Pushwoosh's delegate proxy instead of assigning it to UNUserNotificationCenter directly. The proxy fans every delegate callback out to all registered handlers, so both SDKs keep working.

Recommended API (iOS SDK 7.0 and newer)

import UIKit
import Pushwoosh
import UserNotifications

@main
class AppDelegate: UIResponder, UIApplicationDelegate, PWMessagingDelegate {

    // Delegate instance for your OTHER push provider.
    let otherPushDelegate = OtherPushProviderDelegate()

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

        // Application code comes from Info.plist (Pushwoosh_APPID) or from
        // Pushwoosh.initialize(withAppCode:). The applicationCode property
        // itself is read-only.
        Pushwoosh.initialize(withAppCode: "XXXXX-XXXXX")
        Pushwoosh.configure.delegate = self

        // ** SOLUTION ** register the other provider's delegate with the proxy
        Pushwoosh.configure.addNotificationCenterDelegate(otherPushDelegate)

        // Initialize your other provider, e.g. Firebase:
        // FirebaseApp.configure()
        // Messaging.messaging().delegate = otherPushDelegate

        Pushwoosh.configure.registerForPushNotifications()

        return true
    }
}

class OtherPushProviderDelegate: NSObject, UNUserNotificationCenterDelegate {
    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        completionHandler([.banner, .sound, .badge])
    }
}

On older SDKs

Before 7.0 the same thing is done through the proxy object directly:

Pushwoosh.sharedInstance().notificationCenterDelegateProxy?.add(otherPushDelegate)

Common mistakes:

• Assigning to notificationCenterDelegateProxy — it is a read-only PWNotificationCenterDelegateProxy, not a slot for your delegate.
• Setting applicationCode or an apiToken property on the shared instance — neither is writable on Pushwoosh. Use Pushwoosh_APPID in Info.plist or Pushwoosh.initialize(withAppCode:).
• Setting UNUserNotificationCenter.current().delegate yourself after Pushwoosh has initialized — that detaches the proxy and reintroduces the conflict.