Good day together,

iam pretty new at swift and also in this forum. First I say what I intend to do and then I show what I have done.

After a FetchedRequest has been made, I would like to make the data records available for all views. I thought it would be best to create an EnvironmentObject that holds the data before passing it to each subview.

Intermediate question: Is this a good approach? Or is there a better way.

As I said, I chose the approach with the EnvironmentObject.

Here is the code:

import SwiftUI
import CoreData

@main
struct TestApp: App {

    @StateObject var persistenceManager = PersistenceManager()
    @StateObject var animalManager = AnimalManager()

    var body: some Scene {
        WindowGroup {
            MainMenu().environmentObject(animalManager)
        }
    }
}

import SwiftUI
import CoreData

struct MainMenu: View {

    @State private var showAnimalDetails: Bool = false
    @Environment(\.managedObjectContext) var moc

    var body: some View {
        NavigationView {
            VStack {
                ListView()
                SlideView()
            }           
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        MainMenu()
    }
}

class AnimalManager: ObservableObject {

    @FetchRequest(entity: MyAnimal.entity(), sortDescriptors: [NSSortDescriptor(key: "name", ascending: true)])
     var listOfAnimals: FetchedResults<MyAnimal>    
}

In the Codeblock below raise the Warning message:

Accessing StateObject's object without being installed on a View. This will create a new instance each time.

struct ListView: View {

    @EnvironmentObject var animalManager: AnimalManager

    var body: some View {
        List(animalManager.listOfAnimals){ animal in
            Text(animal.name!)
        }
    }
}

I struggle on this the whole day. iam not sure i follow the right path. Of course I googled it. I found that it might be because I have to execute the fetch result in a view. The solution approach was that I also pass it to the window group. The answer was marked as "correct", but it still doesn't work.

Does anyone have an idea or can tell me what I should do?

Many thanks in advance and a happy new year

Hi! In this case you cannot use @FetchRequest in the class AnimalManager. It will not work that way.

I found that it might be because I have to execute the fetch result in a view.

That is true so you have to refactor your class similar to this. This example passes in moc because you might pass in a different NSManagedObjectContext when previewing your SwiftUI vew. If this is not important to you then you can also just initialize a moc in the initializer and not pass it in.

class AnimalManager: ObservableObject {
    let moc: NSManagedObjectContext
    @Published var listOfAnimals: [AnimalEntity] = []

    init(moc: NSManagedObjectContext) {
      self.moc = moc
    }

    func fetch() {
    // Every entity has a built-in fetchRequest function that returns a fetch request object for you
      let request = AnimalEntity.fetchRequest()

      request .sortDescriptors = [NSSortDescriptor(keyPath: \AnimalEntity.name, ascending: true)]

      if let listOfAnimals = try? moc.fetch(request) {
        self.listOfAnimals = listOfAnimals
    }
}

Then you can use it something like this.

@main
struct TestApp: App {

    let moc = PersistantManager().persistentContainer.viewContext

    var body: some Scene {
        WindowGroup {
            MainMenu(listOfAnimals: AnimalManager(moc: moc))

            // for injection 
              .environmentObject(AnimalManager(moc: moc))
        }
    }
}

struct MainMenu: View {

  @StateObject var listOfAnimals: AnimalManager

    var body: some View {
        NavigationView {
            VStack {
                ListView()
                SlideView()
            }           
        }
        .task {
          listOfAnimals.fetch()
        }
    }
}

or you can inject AnimalManager to the environment and access it from there as well.

Thanks to you both.

And a special thanks to Obelix. I like SwiftData. :)

Everything works immediately. And most importantly, it works the way I want it to.