Custom UI controls are extremely useful when you need some new functionality in your app — especially when they’re generic enough to be reusable in other apps. This custom control tutorial covers the creation of a control kind of like a circular slider inspired by a control knob, such as those found on a mixer.
This is a companion discussion topic for the original entry at https://www.raywenderlich.com/82058/custom-control-tutorial-ios-swift-reusable-knob