How to trigger an alert asking for permission to use Touch ID and FaceID?

Question

iOS

I use in my program two ways to enter touchID and faceID. But I don't like the fact that when I first enter the application, a system alert is called asking to allow the use of touchID/faceID. I'd like to call this alert myself to resolve this in advance.
How to do it?

Answer 1

What do you mean "in advance"? You just said that "the first time you enter the application, the system alert is called." When else in advance?
Answer: In order to request permission, after enabling the option in the settings, immediately launch touchID. Otherwise, it won't ask.