All sample code in this book was written in Swift 4.2 with Xcode 10.0 on a Mac running macOS Mojave. To follow along with all the examples in this book you must have at least Xcode 10.0 installed on your machine. It is recommended that you also have at least macOS Mojave installed on your Mac because not all code samples are compatible with older versions of macOS.
This book assumes that you are somewhat familiar with Swift and iOS development. If you have no experience with Swift at all, it is recommended that you skim through Apple's Swift manual and go over the basics of iOS development. You don't have to be an expert on iOS development yet, but a solid foundation won't hurt you since the pacing of the book is aimed at somewhat experienced developers.