Hello, I can do that seting the managed object context in my BookwormApp.swift (what can we call this kind of document- *App.swift?) follow the article.And i want to see the same effect in Xcode's Swift previews, but i didn't know how to inject a managed object context into preview struct. The article said:

Tip: If you’re using Xcode’s SwiftUI previews, you should also inject a managed object context into your preview struct for ContentView.

My code:

struct Day53_03: View {
    @FetchRequest(sortDescriptors: []) var students: FetchedResults<Student>

    @Environment(\.managedObjectContext) var moc

    var body: some View {
        VStack{
            List(students){student in
                Text(student.name ?? "Unknown")
            }

            Button("Add") {
                let firstNames = ["Ginny", "Harry", "Hermione", "Luna", "Ron"]
                let lastNames = ["Granger", "Lovegood", "Potter", "Weasley"]

                let chosenFirstName = firstNames.randomElement()!
                let chosenLastName = lastNames.randomElement()!

                // more code to come
                let student = Student(context: moc)
                student.id = UUID()
                student.name = "\(chosenFirstName) \(chosenLastName)"

                try? moc.save()
            }
        }
    }
}

struct Day53_03_Previews: PreviewProvider {

    static var previews: some View {
        Day53_03()
    }
}

So,i want wo know how to set up a managed object context in preview struct.

Thank you for trying to help me.

Fly0strich,thank you for your reply, i do it as you said, then it can work what i want.