Shared iPad Touch ID

Quoting off the 'net...

"A scenario many developers may encounter when implementing Touch ID is that a user may have multiple accounts or users on the same device using your app. This is especially true now that four out of five devices in the iPad lineup have a Touch ID sensor for fingerprint authentication, and iPads are commonly shared among many users. Despite this reality, there can only be one Touch ID user per device, so it’s critical to demonstrate this clearly to the user. (Admittedly, users can save multiple fingerprints in Settings, each of which will work to authenticate them. For shared devices, multiple users might each save one of their fingerprints to the shared device, but the system typically assumes one primary user—and it’s easiest for apps to do the same.) The most logical approach to this problem is:

1. Once prompting for Touch ID, apps should include in the prompt message the name of the account they are logging into, in order to clearly demonstrate which account the Touch ID authentication is associated with.
2. When logging into an account that is not the Touch ID–associated account, ensure that users have the ability to switch Touch ID to their current account. Apps can accomplish this by checking username entered versus username stored and, if necessary, display appropriate messaging asking if they want to change their Touch ID–associated account.
3. Make sure the toggle displaying the Touch ID enabled state is synced to the current account, not the status of Touch ID on the phone. Make sure the Touch ID username is the current username logged in, if not, then the Touch ID toggle should be set to off. Furthermore, if the user then enables Touch ID, apps should give the user similar messaging about changing their Touch ID–associated account."