> Apple provided a fully functional demo app called Sketch which showed important architectural patterns like undo/redo. When developing my first Cocoa app, I’d

> Apple provided a fully functional demo app called Sketch which showed important architectural patterns like undo/redo. When developing my first Cocoa app, I’d basically go see how Sketch.app implemented something and copied the approach. For reference: https://developer.apple.com/library/archive/samplecode/Sketch/Introduction/Intro.html#//apple_ref/doc/uid/DTS40011772 https://developer.apple.com/library/archive/samplecode/Sketc... This was a tad difficult to find due to the aforementioned commercial Mac app called Sketch.