I have an iOS game. And i want to reward a player after his friend on Facebook has accepted his invite to play the game. Now i see only one way to do this. Firstly we save recipient fb IDs and then from time to time check wether that recipients are connected to Facebook from the game(we check is_app_user flag), and if so we reward our sender. But in this case we can not identify wether recipient started to play by accepting friend request or found the game by himself.
Maybe someone has experience in this area and can share better strategy how to track users who accepted friend request to play the game?
