Hi.

Maybe it's elementary, but I can't figure out how to do it. After studying the One-to-many relationships with Core Data lesson, I created a project by slightly changing the display of the view and adding a window for creating a new candy.

How can I save this candy to the country I went to via the NavigationLink?

List {
            ForEach(countries, id: \.self) { country in
                NavigationLink(country.wrappedFullName) {
                    Form {
                        ForEach(country.candyArray,id: \.self) { candy in
                            Text(candy.wrappedName)
                        }
                        Button("Add Candy") {
                            presentingAddNewCandySheet.toggle()
                        }
                    }
                }
            }
        }

I create a new candy through

TextField("Candy name", text: $name)

The data is saved and a new candy appears, but a new country is also created

Button("Add") {
        let candy = Candy(context: moc)
        candy.name = name

        candy.origin = Country(context: moc) /// ?
        candy.origin?.shortName = "UK" /// ?
        candy.origin?.fullName = "United Kingdom" /// ?

        try? moc.save()
    }

What should be instead of these lines?

Thanks for the possible answers!

make a small func for your button with a candy: Candy parameter, try the below:

func addCandy(country: Country) {
let candy = Candy(context: moc)
        candy.name = name

        candy.origin = country

        try? moc.save()
}

Your updated Button in the toggle sheet:

Button("Add") {
        addCandy(country: country) // The country here is the one taken from your "ForEach(countries, id: \.self) { country in"
    }

Yes, I made a picker for selection, it did not work correctly. And after your answer, I thought again and found the problem. Now everything seems to be working!

Here is the code for the picker and save (may be useful to someone)

@State var selection: Country?

Picker("Country", selection: $selection) {
    ForEach(countrys, id: \.self) { (country: Country) in
        Text(country.fullName!)
            .tag(country as Country?)
    }
}

Button("Add") {
    let candy = Candy(context: moc)
    candy.name = name
    candy.origin = Country(context: moc)
    candy.origin?.shortName = selection?.shortName
    candy.origin?.fullName = selection?.fullName ?? "New Country"

    try? moc.save()
}

Tried the second answer option from @Bnerd too

Button("Add") {
   addCandy(country: country) /// Error: "Cannot find 'country' in scope"
}

I add var country = Country()

When you save Candy, the application crashes with a response:

Thread 1: "Illegal attempt to establish a relationship 'origin' between objects in different contexts...

Let's say your pop up sheet is like the below:

struct AddCandyView: View {
    @Environment(\.managedObjectContext) var moc
    var selectedCountry: Country
    @State var name = ""

    var body: some View {
        VStack{
            TextField("Candy name", text: $name)
            Button("Add") {
                addCandy(country: selectedCountry)
            }
        }
    }

    func addCandy(country: Country) {
        let candy = Candy(context: moc)
        candy.name = name

        candy.origin = country

        try? moc.save()
    }
}

your .sheet should be within the Foreach like this:

NavigationLink(country.wrappedFullName) {
                            //previous code here.
                        }
                        .sheet(isPresented: $presentingAddNewCandySheet) {
                            AddCandyView(selectedCountry: country)
                        }