These are the Starter files and the Final files for the Ray Wenderlich tutorial in Swift 4, iOS 11, XCode 9, so needs updating ...woe is me.
Original Tutorial here: https://www.raywenderlich.com/5294-how-to-make-a-custom-control-tutorial-a-reusable-knob
Date: March 19th 2019. Robert Chalmers
Robert Chalmers https://robert-chalmers.uk [email protected] @R_A_Chalmers