Project 11 (Bookworm) problems

@davidexcell

Mar '20

Hi, stuck on a problem here - help welcome.

I've worked through the example step by step to build the Bookworm app, got as far as "Creating books with Core Data". The code won't compile though.

I've tried on two different Macs (rebooted) and I've also tried the completed tutorial code as well as the partial example I've built up. Won't work either way.

The compiler error messages I'm getting (from the completed Project 11 tutorial) are: 1) ContentView: "Use of undeclared type 'Book' 2) AddBookView: "Use of unresolved identifier 'Book' 3) DetailView: both of the above

Any insights?

Thanks

@Gakkienl HWS+

Mar '20

Might help to add some code to your post!

@davidexcell

Mar '20

I've pasted in some of the code below for ContentView of Project 11 (Bookworm) - this is from the tutorial files downloaded from GitHub at https://github.com/twostraws/HackingWithSwift. This particular project is in the SwiftUI section.

The Buildtime error message shows up at @FetchRequest and says "Use of undeclared type 'Book'. I've checked that Book is defined as an entity in the xcdatamodeld file.

import SwiftUI

struct ContentView: View { @Environment(.managedObjectContext) var moc @FetchRequest(entity: Book.entity(), sortDescriptors: [ NSSortDescriptor(keyPath: \Book.title, ascending: true), NSSortDescriptor(keyPath: \Book.author, ascending: true) ]) var books: FetchedResults<Book>

@State private var showingAddScreen = false

var body: some View {
     NavigationView {
        List {
            ForEach(books, id: \.self) { book in
                NavigationLink(destination: DetailView(book: book)) {
                    EmojiRatingView(rating: book.rating)
                        .font(.largeTitle)

                    VStack(alignment: .leading) {
                        Text(book.title ?? "Unknown Title")
                            .font(.headline)
                        Text(book.author ?? "Unknown Author")
                            .foregroundColor(.secondary)
                    }
                }
            }
            .onDelete(perform: deleteBooks)
        }
        .navigationBarTitle("Bookworm")
        .navigationBarItems(leading: EditButton(), trailing: Button(action: {
            self.showingAddScreen.toggle()
        }) {
            Image(systemName: "plus")
        })
        .sheet(isPresented: $showingAddScreen) {
            AddBookView().environment(\.managedObjectContext, self.moc)
        }
    }
}

etc

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	@davidexcell Mar '20 Sorry, I applied some formatting to the problematic line of code and that messed things up - see all original code in ContentView below... // // ContentView.swift // Project11 // // Created by Paul Hudson on 17/02/2020. // Copyright © 2020 Paul Hudson. All rights reserved. // import SwiftUI struct ContentView: View { @Environment(.managedObjectContext) var moc @FetchRequest(entity: Book.entity(), sortDescriptors: [ NSSortDescriptor(keyPath: \Book.title, ascending: true), NSSortDescriptor(keyPath: \Book.author, ascending: true) ]) var books: FetchedResults<Book> @State private var showingAddScreen = false var body: some View { NavigationView { List { ForEach(books, id: \.self) { book in NavigationLink(destination: DetailView(book: book)) { EmojiRatingView(rating: book.rating) .font(.largeTitle) VStack(alignment: .leading) { Text(book.title ?? "Unknown Title") .font(.headline) Text(book.author ?? "Unknown Author") .foregroundColor(.secondary) } } } .onDelete(perform: deleteBooks) } .navigationBarTitle("Bookworm") .navigationBarItems(leading: EditButton(), trailing: Button(action: { self.showingAddScreen.toggle() }) { Image(systemName: "plus") }) .sheet(isPresented: $showingAddScreen) { AddBookView().environment(\.managedObjectContext, self.moc) } } } func deleteBooks(at offsets: IndexSet) { for offset in offsets { // find this book in our fetch request let book = books[offset] // delete it from the context moc.delete(book) } // save the context try? moc.save() } } struct ContentView_Previews: PreviewProvider { static var previews: some View { ContentView() } } 3
	@Gakkienl HWS+ Mar '20 Obviously it can't seem to find your type Book. Can have various reasons. Try and clean your project: CMD-SHIFT-K and then build your project: CMD-B Does that help? If not, not a typo somewhere ? 3
	@davidexcell Mar '20 Thanks, I'd already tried cleaning and rebuilding and still got the same problem. The project is directly from Paul's Hacking With Swift(UI) course so probably the simplest thing would be for me to message him directly in a day or so if no-one on the forum has had this issue and found a solution. 3
	@Sangsom Mar '20 I've copied your code and used in my project, the only problem I got is in this line: `@Environment(.managedObjectContext) var moc` You need to add `backslash` in order to compile. `@Environment(\.managedObjectContext) var moc` But actually for this one I'm getting different error, Generic parameter 'Value' could not be inferred. 3
	@NigelGee HWS+ Mar '20 If your first bit of code that you did not put in codeformat, looks like this `struct ContentView: View { @Environment(\.managedObjectContext) var moc @FetchRequest(entity: Book.entity(), sortDescriptors: [ NSSortDescriptor(keyPath: \Book.title, ascending: true), NSSortDescriptor(keyPath: \Book.author, ascending: true) ]) var books: FetchedResults<Book>` then check that when click on Book ENTITIES and check the right hand panel the Entity Name has Book, Class Name has Book and Codegen is Class Definition Did you set up project with the Core Data ticked. If not you will have to add some code in AppDelegate.swift and SceneDelegate.swift 3
	@davidexcell Mar '20 Thanks, I've confirmed that the entity name, class name and codegen are as you said. Also, the project was set up with Core Data ticked. Sadly, the problem remains. 3
	@NigelGee HWS+ Mar '20 Sorry to hear that I was trying to create the errors and when changed these fields give me the error you got. I hope that you get an answer. 3
	@PJCCMC Mar '20 I had the same error - with the “How you combine the Core Data and Swift UI" section in Bookworm while replicating Paul's student example. In the end fully closing Xcode then restarting it solved the problem. – Hope this helps. 3
	@krisnielsen Apr '20 I've just been trying to solve this myself, and what worked for me was opening the Inspector for `Bookworm.xcdatamodeld` and unchecking then checking the checkbox for Bookworm under Target Membership. Hope this helps anyone else running into the issue. 3
	@GlenLam Jun '20 I just stumbled upon a weird bug (tested in Xcode 11.1 and 13.1 in Mojave). If the project name has a space dash space, then the project won't build. For example, I've been naming my projects like this: Project 11 - Bookworm. No matter what, it won't build. When I take out a space on either side of the dash in a new project, then it would work. Granted, I still needed to do the clean/restart Xcode/build dance, but at least it would compile after that. Hope that helps anyone that may have trouble with Core Data. 3
	@BasTheDeveloper Jun '20 Seems a similar problem as dicussed in https://www.hackingwithswift.com/forums/100-days-of-swiftui/day-53-bookworm-use-of-undeclared-type-student-error-when-using-core-data/1265 Try the solution byaruhaf proposed in that thread. 3

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