I applied CloudKit to CoreData in SwiftUI and found that the real-time data works well between the simulator and the real device.

Deleting iCloud data from the simulator or real device Settings -> iCloud -> Manage Account Storage causes two issues.

1. if the app is running when you clear the icloud data in settings, the app still has the data, and when I exit the app and run it again, the data disappears.

2. after clearing icloud data in settings, there is no real-time data synchronization between the simulator and the real device - I must go to background mode and come back to the app for it to be reflected. -> Delete and reinstall the app on the simulator and real device to get real-time data integration again.

If anyone has experienced this issue, I would appreciate your help. Thank you.

import CoreData
import Foundation

final class DataController: ObservableObject {
    let cloudKitContainer: NSPersistentCloudKitContainer

    init() {
        cloudKitContainer = NSPersistentCloudKitContainer(name: "Item")
        guard let description = cloudKitContainer.persistentStoreDescriptions.first else {
            fatalError("Failed to init persistent container")
        }
        description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
        description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)

        cloudKitContainer.viewContext.automaticallyMergesChangesFromParent = true
        cloudKitContainer.viewContext.mergePolicy = NSMergePolicy.mergeByPropertyObjectTrump

        cloudKitContainer.loadPersistentStores { description, error in
            if let error {
                print("Faild Load CoreData. \(error.localizedDescription)")
                return
            }
        }
    }
}