Basic Swift sample app for collecting user info for signup, create account or the like and validating its acceptability before enabling the Signup button. It creates a UserInfo class that uses Combine to provide a clean easy way to validate the input. Using Combine and a separate class removes validation code from the view controller. UIKit requires some initialization that SwiftUI doesn't because it was retro-fitted for publishing. But that can go into an extension and still a very clean view controller.
Signin-UIKitandCombine is licensed under the MIT License. See the LICENSE file for more information, but basically this is sample code and you can do whatever you want with it.