Shared app to trigger iOS code

Hi, I have a need for a shared app to trigger code in an iOS project.

All code to login resides in the shared app so I need to call iOS specific binding project method once the user is successfully in. Is this possible?

My original thought was to call Twilio.Register within the RegisteredForRemoteNotifications override but that occurs on app launch rather than after logging in. I can't think of any other way apart from making platform specific login code.