Today started just like any other day. You sat down at your desk, took a sip of coffee and opened up Xcode to start a new project. But wait! The similarities stop there. Today, we will try to build for a different platform! Don’t be afraid. I know you are comfortable there on your iOS island, knocking out iOS applications, but today begins a brand new adventure. Today is the day we head on over to macOS development, a dark and scary place that you know nothing about.
The good news is that developing for macOS using Swift has a lot more in common with iOS development than you realize. To prove this, I will walk you through building a simple screen-annotation application. Once we complete it, you will realize how easy it is to build applications for macOS.
Source: Smashing Magazine