We're working on a game in which we do an automatic sign-up in the background the first time a user plays. We sign-up the user with a username and password combo based on the device id. We handle future logins based on saved credentials on the device.
If the user tries to play from another device, however, we'd like to retrieve his user profile based on a Game Center id or Facebook id saved to his profile. The problem is that we can't query the user collection for a particular Game Center or Facebook id before the user is logged in on the new device. I understand that you can't query without an active user, so is there some other way to manage users playing on multiple devices without making users choose usernames and passwords?
almost 10 years ago
If you have detected a Facebook profile on the device, and have linked user accounts to Facebook in your backend, then you could attempt to perform a Facebook login with that profile and only perform the implicit registration if that login fails?