Can't set TouchId reason at runtime

[phampton24]

Hi

I have an app that requires the user to authenticate against a server with user credentials before accessing the app. I am using a combination of Pin and/or TouchId depending on device capabilities so that the user doesn't have to manually enter their credentials each time.

When using this control with TouchId, I'd like to have a way of injecting the TouchId reason at run time. I can't use the static .strings file because I need to include data in the reason that I'll only know at run time.