You should import the Foundation framework in order to work with the UUID class like this:
import Foundation
You can find the book’s current version errata page over here:
We will definitely take your valuable feedback into account when and while we update the book for Swift 4, Xcode 9 and iOS 11 after all for sure and for good indeed. In the meantime, please post any other questions or issues regarding the book in its corresponding thread over here instead:
Thank you! :]