Error: Thread 1: "executeFetchRequest:error: A fetch request must have an entity." - swiftui

Question

I'm trying to use CoreData in my Xcode-project (SwiftUI). I've created a Player entity and wanna use it in my View called "YouView". But when I'm trying to fetch the data, I get the error from Title. My app is called Dart Tools. My Application Language is German, so don't worry if you don't understand everything of the ui :).
Thanks for helping!
I already tried the .shared variant - same error
This is my .xcdatamodeld file (called DataModel.xcdatamodeld)
This is the Code of my DataController file:
import Foundation
import CoreData
class DataController: ObservableObject {
let container = NSPersistentContainer(name: "DataModel")
init() {
container.loadPersistentStores { desc, error in
if let error = error {
print("Daten wurden nicht geladen: \(error.localizedDescription)")
}
}
}
func save(context: NSManagedObjectContext) {
do {
try context.save()
print("Daten wurden gespiechert!")
} catch {
print("Daten konnten nicht gespeichert werden.")
}
}
func addPlayer(name: String, isUser: Bool, context: NSManagedObjectContext) {
let player = Player(context: context)
player.id = UUID()
player.name = name
player.isUser = isUser
save(context: context)
}
func editPlayerName(player: Player, name: String, context: NSManagedObjectContext) {
player.name = name
save(context: context)
}
}
Here is my DartToolsApp.swift file:
import SwiftUI
//The error is here:
#main
struct DartToolsApp: App {
#StateObject private var userDefaults = UserDefaults()
#StateObject private var dataController = DataController()
var body: some Scene {
WindowGroup {
ContentView()
.environment(\.managedObjectContext, DataController().container.viewContext)
.environmentObject(UserDefaults())
}
}
}
This is the file where I want to use the Data:
Btw, this view is a piece of a TabView.
import SwiftUI
import CoreData
struct YouView: View {
#EnvironmentObject var userDefaults: UserDefaults
// I guess the error is because of this line:
#FetchRequest(sortDescriptors: []) var players: FetchedResults<Player>
#Environment(\.managedObjectContext) var managedObjectContext
var body: some View {
NavigationStack {
Form {
}
.navigationTitle("\(findUser()) (Du)")
}
}
func findUser() -> String {
if let index = players.firstIndex(where: { $0.isUser }) {
let output = players[index].name!
return output
}
else {
return ""
}
}
}
This is the code to create the user:
DataController().addPlayer(name: nameText, isUser: true, context: managedObjectContext)
Wow, that was a lot of code. I hope you can help me!

Answer 1

You are creating new instances of DataController everywhere which is a problem in itself but what think causes your particular error is when you assign the \.managedObjectContext environment variable.
So instead of creating a new instance you should use your #StateObject instance instead.
So change this in the App code
var body: some Scene {
WindowGroup {
ContentView()
.environment(\.managedObjectContext, dataController.container.viewContext)
}
}