A few folks have noted this in the Errata thread as well – but I’d say it’s less of a typo and more of a potential showstopper for people who are new to SwiftUI.
After digging through the sample code and piecing things together on my own, I’m doing okay. But I have to say… the Kuchi app seems pretty sweet and I can tell a lot went in to making it. A more thorough walkthrough of building it would be great for both the book’s structure and it’s goal of teaching SwiftUI.