swift Debugging IBDesignables @IBDesignable views are great. They let you visualize your custom embedded views, making it easy to see what your UI will look like once the app runs. Unfortunately many people don't use them
swift Marzipan - UIKit on macOS EDIT: July 26, 2019 WWDC 2019 brought us SwiftUI and Catalyst. As such this article is not relevant anymore. Feel free to look at the documentation provided by Apple and have fun with