Push notification system alert

Hey there!
I’ve been using ionic 3 for my app. Everything is working perfectly but I’m facing an issue related to fcm push notification. Fcm notification is implemented and is working like a charm the only issue I’m facing is the system alert to allow notification.
I am getting the system alert to allow/don’t allow notification even before the user is logged in however, I want the alert to prompt once the user sign in/sign up. I need to fix it on ios platform. Any help will be appreciated.

I want this alert after user login or register.

Register ( FCM registration request ) your device , after signing up or after logging in thats the way

Already followed the approach you suggested, but no luck here!