Hi, when creating a new book in the Bookworm project, if i don't touch the genre picker and let it go with the default value (Fantasy), when i go to check the detail view, it doesn't appear (neither image or text). But if i click the picker, choose another value and then click "Fantasy" it appears.

My DetailView code:

import CoreData
import SwiftUI

struct DetailView: View {

    let book: Book

    var body: some View {
        ScrollView {
            ZStack(alignment: .bottomTrailing) {
                Image(book.genre ?? "Fantasy")
                    .resizable()
                    .scaledToFit()

                Text(book.genre?.uppercased() ?? "FANTASY")
                    .font (.caption)
                    .fontWeight(.black)
                    .padding(8)
                    .foregroundColor(.white)
                    .background(.black.opacity(0.75))
                    .clipShape(Capsule())
                    .offset(x: -5, y: -5)
            }

            Text(book.author ?? "Unknown author")
                .font(.title)
                .foregroundColor(.secondary)

            Text(book.review ?? "No review")
                .padding()

            RatingView(rating: .constant(Int(book.rating)))
                .font(.largeTitle)
        }
        .navigationTitle(book.title ?? "Unknown Book")
        .navigationBarTitleDisplayMode(.inline)
    }
}

struct DetailView_Previews: PreviewProvider {

    static let moc = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)

    static var previews: some View {

        let book = Book(context: moc)
        book.title = "Test book"
        book.author = "Test author"
        book.genre = "Fantasy"
        book.rating = 4
        book.review = "This was a great book; I really enjoyed it."

        return NavigationView {
            DetailView(book: book)
        }
    }
}

Hi. This is ok. Because later in the course you will add validation and your "Save" button won't be active until all fields are filled. If you look at your AddBookView you can see that you genre is not nil when you create it but an empty string i.e. "". So when you create your book empty string is assinged to your book genre NOT nil. And when you go to DetailView as there are no genre with empty string and no image name with empty string it cannot find anything so it doesn't show those pieces. But once you add validation to your save button later in the project you won't be able to save it unless all data is filled.