I’m attempting to add local persistence to items fetched from CloudKit using Core Data in my app, but I’m not achieving the desired behavior. Here’s what I aim to accomplish:

1. User opens the app.
2. Fetch items from CloudKit.
3. Display the fetched items.
4. Save the fetched items to Core Data.

5. User closes and reopens the app.
6. Display the saved items from Core Data, as before.
7. Sync with CloudKit and smoothly update the display if there are any changes.

My approach below is wrong because, as a SO user mentioned: “In SwiftUI the View structs are the view model already you shouldn’t try to use objects or will run into major issues. StateObject is for something else.” I am seeking guidance on the correct way to handle this.

class CloudKitViewModel: ObservableObject {
    @Published var items: [Item] = []
    @Published var selectedItem: Item?
    private var database = CKContainer.default().publicCloudDatabase
    private let persistentContainer: NSPersistentContainer

    init() {
        let container = CKContainer(identifier: "iCloud.com.user.my.project")
        self.database = container.publicCloudDatabase
        
        // Set up Core Data
        persistentContainer = NSPersistentContainer(name: "Model")
        persistentContainer.loadPersistentStores { description, error in
            if let error = error {
                fatalError("Unable to load persistent stores: (error)")
            }
        }
        
        loadSavedItems()
        fetchItems()
    }

    func fetchItems() {
        let query = CKQuery(recordType: "Item", predicate: NSPredicate(value: true))
        database.perform(query, inZoneWith: nil) { records, error in
            if let records = records {
                DispatchQueue.main.async {
                    self.items = records.map { record in
                        Item(
                            id: record.recordID,
                            city: record["City"] as? String ?? ""
                        )
                    }
                    self.saveItemsToCoreData()
                }
            } else if let error = error {
                print("Error fetching records: (error.localizedDescription)")
            }
        }
    }
    
    private func loadSavedItems() {
        let context = persistentContainer.viewContext
        let fetchRequest: NSFetchRequest<Model> = Model.fetchRequest()
        
        do {
            let itemEntities = try context.fetch(fetchRequest)
            self.items = itemEntities.map { entity in
                Item(
                    id: CKRecord.ID(recordName: entity.id ?? ""),
                    city: entity.city ?? ""
                )
            }
        } catch {
            print("Failed to fetch items from Core Data: (error)")
        }
    }

    private func saveItemsToCoreData() {
        let context = persistentContainer.viewContext
        
        // Remove old data
        let fetchRequest: NSFetchRequest<NSFetchRequestResult> = Model.fetchRequest()
        let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
        
        do {
            try context.execute(deleteRequest)
        } catch {
            print("Failed to delete old items from Core Data: (error)")
        }
        
        // Save new data
        items.forEach { item in
            let entity = Model(context: context)
            entity.id = item.id.recordName
            entity.city = item.city
        }
        
        do {
            try context.save()
        } catch {
            print("Failed to save items to Core Data: (error)")
        }
    }
}

Here’s how items are displayed to the user on startup:

struct MyView: View {
    @StateObject private var viewModel = CloudKitViewModel()
    var body: some View {
        NavigationView {
            VStack {
                List {
                    Section {
                        ForEach(viewModel.items) { item in
                            ItemRow(
                                item: item
                            )
                        }
                    }
                }
            }
        }
    }
}

struct Item: Identifiable {
    var id: CKRecord.ID
    var city: String
}

struct ItemRow: View {
    var item: Item
    var body: some View {
        HStack {
            Text(item.city)
        }
    }
}