Warning: As biometric fingerprint methods may request user to present its fingerprint through the TouchId UI, it is recommended that developer avoid to call these methods on the main thread, to limit the risk of blocking or freezing the handset. Developer should use the biometric fingerprint methods on a separate thread, as describe in the example below

// dispatch a new thread to deactivate non silently dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{

[token deactivateAuthModeWithInput:bioFpAuthInput error:&error];

//some logic

//update UI dispatch_async(dispatch_get_main_queue (), ^{ … } }

Warning: In iOS8, two calls in a row of biometric methods; using the TouchID UI to authenticate the user, will not work. The second call will return an error code without presenting the TouchID UI to the user. So application should respect this constraint, and for example, not try to compute two OTP consecutively. However, if it is really needed, developers can add a sleep instruction (of 1 second or more) between the two biometric calls to make it work.