I have several apps that use CoreData / iCloud syncing and they all receive a slew of update/change/insert/delete/etc notifications when they start and sometimes as they are running without any changes to the underlying data. When a new item is added or deleted, it appears that I get notifications for everything again. Even the number of notifications are not consistent.
My question is, how do I avoid this? Is there a cut-off that can be applied once I'm sure I have everything up to date on a device by device basis.
Persistence
import Foundation
import UIKit
import CoreData
struct PersistenceController {
let ns = NotificationStuff()
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
for _ in 0..<10 {
let newItem = Item(context: viewContext)
newItem.stuff = "Stuff"
newItem.timestamp = Date()
}
do {
try viewContext.save()
} catch {
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
return result
}()
let container: NSPersistentCloudKitContainer
init(inMemory: Bool = false) {
container = NSPersistentCloudKitContainer(name: "TestCoreDataSync")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
}
class NotificationStuff
{
var changeCtr = 0
init()
{
NotificationCenter.default.addObserver(self, selector: #selector(self.processUpdate), name: Notification.Name.NSPersistentStoreRemoteChange, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(contextDidSave(_:)), name: Notification.Name.NSManagedObjectContextDidSave, object: nil)
NotificationCenter.default.addObserver(self, selector: #selector(contextObjectsDidChange(_:)), name: Notification.Name.NSManagedObjectContextObjectsDidChange, object: nil)
}
@objc func processUpdate(_ notification: Notification)
{
//print(notification)
DispatchQueue.main.async
{ [self] in
observerSelector(notification)
}
}
@objc func contextObjectsDidChange(_ notification: Notification)
{
DispatchQueue.main.async
{ [self] in
observerSelector(notification)
}
}
@objc func contextDidSave(_ notification: Notification)
{
DispatchQueue.main.async
{
self.observerSelector(notification)
}
}
func observerSelector(_ notification: Notification) {
DispatchQueue.main.async
{ [self] in
if let insertedObjects = notification.userInfo?[NSInsertedObjectsKey] as? Set<NSManagedObject>, !insertedObjects.isEmpty
{
print("Insert")
}
if let updatedObjects = notification.userInfo?[NSUpdatedObjectsKey] as? Set<NSManagedObject>, !updatedObjects.isEmpty
{
changeCtr = changeCtr + 1
print("Change \(changeCtr)")
}
if let deletedObjects = notification.userInfo?[NSDeletedObjectsKey] as? Set<NSManagedObject>, !deletedObjects.isEmpty
{
print("Delete")
}
if let refreshedObjects = notification.userInfo?[NSRefreshedObjectsKey] as? Set<NSManagedObject>, !refreshedObjects.isEmpty
{
print("Refresh")
}
if let invalidatedObjects = notification.userInfo?[NSInvalidatedObjectsKey] as? Set<NSManagedObject>, !invalidatedObjects.isEmpty
{
print("Invalidate")
}
let mainManagedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
guard let context = notification.object as? NSManagedObjectContext else { return }
// Checks if the parent context is the main one
if context.parent === mainManagedObjectContext
{
// Saves the main context
mainManagedObjectContext.performAndWait
{
do
{
try mainManagedObjectContext.save()
} catch
{
print(error.localizedDescription)
}
}
}
}
}
}
ContentView
import SwiftUI
import CoreData
struct ContentView: View {
@State var stuff = ""
@Environment(\.managedObjectContext) private var viewContext
@FetchRequest(
sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)],
animation: .default)
private var items: FetchedResults<Item>
var body: some View {
VStack
{
TextField("Type here", text: $stuff,onCommit: { addItem(stuff: stuff)
stuff = ""
})
List {
ForEach(items) { item in
Text(item.stuff ?? "??")
}
.onDelete(perform: deleteItems)
}
}.padding()
}
private func addItem(stuff: String) {
withAnimation {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
newItem.stuff = stuff
do {
try viewContext.save()
} catch {
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
private func deleteItems(offsets: IndexSet) {
withAnimation {
offsets.map { items[$0] }.forEach(viewContext.delete)
do {
try viewContext.save()
} catch {
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
}
private let itemFormatter: DateFormatter = {
let formatter = DateFormatter()
formatter.dateStyle = .short
formatter.timeStyle = .medium
return formatter
}()
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView().environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
The database has an Item entity with a timestamp field and a string field named stuff.
