In my app, previews will crash when isStoredInMemoryOnly is set to false in the main file, but works fine when it's set true. I have tried adding inMemory = true to the Previews and following some of the examples on this site but nothing works.

This is my main file

import SwiftUI
import SwiftData

@main
struct MyApp: App {
    var sharedModelContainer: ModelContainer = {
        let schema = Schema([
            Card.self,
        ])
        // CHANGE INMEMORY TO FALSE
        let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: true)

        do {
            return try ModelContainer(for: schema, configurations: [modelConfiguration])
        } catch {
            fatalError("Could not create ModelContainer: \(error)")
        }
    }()

    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .modelContainer(sharedModelContainer)
    }
}

Here is ContentView whose Preview crashes:

import SwiftUI
import SwiftData

struct ContentView: View {
    @Environment(\.modelContext) private var modelContext
    @Query var cards: [Card]

    var body: some View {
        NavigationStack {
            VStack {
                // some stuff
            .background(Image("Background").brightness(-0.25))
        }
        .tint(Color(red: 1, green: 1, blue: 0))
        .onAppear(perform: {
            if UserDefaults.standard.bool(forKey: "notfirst") {
                print("not first")
                return
            }
            print("first")
            parseInitialData()
            UserDefaults.standard.setValue(true, forKey: "notfirst")
        })
    }

    func parseInitialData() {
        guard let filename = Bundle.main.path(forResource: "data", ofType: "txt") else {
            print("FILE NOT FOUND")
            return
        }
        let contents = try! String(contentsOfFile: filename)
        let entries = contents.components(separatedBy: "\n")
        var i = 0
        for entry in entries {
            let sides = entry.components(separatedBy: ":")
            if sides.count == 1 { continue }
            modelContext.insert(Card(indexInBox: i, level: 1, char: sides[0], solution: sides[1]))
            i += 1
        }
    }

}
#Preview {
    ContentView()
        .modelContainer(for: Card.self)
}