Since my last question (here toggle between local and iCloud CoreData store) I was able to make a lot of progress.
I am switching between NSPersistentCloudKitContainer and NSPersistenttContainer
But...
When I switch off the CloudKit synchronization and update the container, the sync is still active.After restarting the app manually the sync is deactivated.
This is the same problem some people are describing in the comments here...
CoreData+CloudKit | On/off iCloud sync toggle
But I wasn't able to find a solution.
MyApp.swift
#main
struct MyApp: App {
#StateObject private var persistenceContainer = PersistenceController.shared
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(CoreBluetoothViewModel())
.environment(\.managedObjectContext, persistenceContainer.container.viewContext)
}
}
}
PersistenceController
import CoreData
class PersistenceController: ObservableObject{
static let shared = PersistenceController()
lazy var container: NSPersistentContainer = {
setupContainer()
}()
init() {
container = setupContainer()
}
func updateContainer() {
saveContext()
container = setupContainer()
saveContext()
}
private func setupContainer() -> NSPersistentContainer {
let iCloud = UserDefaults.standard.bool(forKey: "iCloud")
do {
let newContainer = try PersistentContainer.getContainer(iCloud: iCloud)
guard let description = newContainer.persistentStoreDescriptions.first else { fatalError("No description found") }
if iCloud {
newContainer.viewContext.automaticallyMergesChangesFromParent = true
newContainer.viewContext.mergePolicy = NSMergeByPropertyStoreTrumpMergePolicy
} else {
description.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
description.cloudKitContainerOptions = nil
}
description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
newContainer.loadPersistentStores { (storeDescription, error) in
if let error = error as NSError? { fatalError("Unresolved error \(error), \(error.userInfo)") }
}
return newContainer
} catch {
print(error)
}
fatalError("Could not setup Container")
}
private func saveContext() {
do {
try container.viewContext.save()
} catch {
let error = error as NSError
fatalError("ERROR: \(error)")
}
}
}
final class PersistentContainer {
private static var _model: NSManagedObjectModel?
private static func model(name: String) throws -> NSManagedObjectModel {
if _model == nil {
_model = try loadModel(name: name, bundle: Bundle.main)
}
return _model!
}
private static func loadModel(name: String, bundle: Bundle) throws -> NSManagedObjectModel {
guard let modelURL = bundle.url(forResource: name, withExtension: "momd") else {
throw CoreDataModelError.modelURLNotFound(forResourceName: name)
}
guard let model = NSManagedObjectModel(contentsOf: modelURL) else {
throw CoreDataModelError.modelLoadingFailed(forURL: modelURL)
}
return model
}
enum CoreDataModelError: Error {
case modelURLNotFound(forResourceName: String)
case modelLoadingFailed(forURL: URL)
}
public static func getContainer(iCloud: Bool) throws -> NSPersistentContainer {
let name = "LogModel"
if iCloud {
return NSPersistentCloudKitContainer(name: name, managedObjectModel: try model(name: name))
} else {
return NSPersistentContainer(name: name, managedObjectModel: try model(name: name))
}
}
}
Does anyone have any idea how I could solve this problem?
fairly new to SwiftUi still but have been struggling with finding a solution to this problem as well. By the looks of it I’ve been following all of the stackoverflow questions and answers as yourself.
For context I get a very inconsistent result between a iPad and a iPhone with a version of my code which is pretty close to mine, where sometimes it works and I can toggle on and off cloudkit.
However...
After playing around with the code and commenting on and off lines and reading some more, this line of code stood out as a question for me.
description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
surely the answer is in its name. RemoteChangeNotificationPost.
what I have done its put that line in with the
if iCloud {
newContainer.viewContext.automaticallyMergesChangesFromParent = true
newContainer.viewContext.mergePolicy = NSMergeByPropertyStoreTrumpMergePolicy
description.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
}
so it only "Posts Changes" when iCloud is enabled.
now when I toggle off cloudkit. no updates are sent through.
When you toggle it back on, it does require a change to happen on the device to trigger a sync it seams but it I feel its a step closer to a result?
hit me down everyone if im doing anything wrong wouldn't want to be pushing a bad practice but so far.... it works till I find a better solution.
I have a ListView file which can build the preview code fine without the Core Data piece in it. However, when I build that ListView in the ContentView, I got an error that is not shown in the text editor like usual but in the diagnostics window. The error is "A fetch request must have an entity UncaughtExceptionError: [AppName] crashed due to an uncaught exception".
When I run the app in the simulator, the ContentView seems to build fine. (the functions attached to Text("+") don't work either, something about "map table argument is NULL", but one error at a time.)
EDIT: The entities in Core Data are set up as “Class Definition”.
Many many thanks in advance.
struct ListView: View {
#Environment(\.managedObjectContext) var viewContext
#FetchRequest(sortDescriptors: []) var targets: FetchedResults<TargetEntity>
#FetchRequest(sortDescriptors: []) var positives: FetchedResults<PositiveEntity>
var body: some View {
VStack {
HStack {
VStack {
Text("+")
.onAppear{add()}
.onTapGesture (count: 2){
do {
print("error")
increment(targets.first!)
try viewContext.save()
} catch {
print("error")
}
}
.onLongPressGesture {
addPositive()
}
List{
ForEach(positives) { item in
Text(item.title ?? "Unknown Title")
}
.onDelete(perform: deleteItems)
}
}
}
}
}
func add() {
let countnum = TargetEntity(context: viewContext)
countnum.countnum = 0
save()
}
func addPositive(){
let newPositive = PositiveEntity(context: viewContext)
newPositive.title = "Action"
save()
}
private func deleteItems(offsets: IndexSet) {
withAnimation {
offsets.map { positives[$0] }.forEach(viewContext.delete)
do {
try viewContext.save()
} catch {
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
func save() {
do { try viewContext.save() } catch { print(error) }
}
}
struct ListView_Previews: PreviewProvider {
static var previews: some View {
NavigationView{
ListView()//.environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
}
Just faced same issue after updating core data model with new entity, in a project created with core data.
Error happens only to "canvas" preview, with simulator or real devices everything is ok.
Issue resolved for me by adding mock of created model to PersistenceController under the preview var
I don't understand when I try to remove all items by calling viewContext.execute(deleteRequest) SwiftUI doesn't redraw UI.
I see items from sqlite are gone.
struct CloudKitTestView: View {
#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 {
Button("Remove all") {
let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Item")
let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
do {
try viewContext.execute(deleteRequest)
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
List {
ForEach(items) { item in
Text("Item at \(item.timestamp!, formatter: itemFormatter)")
}
.onDelete(perform: deleteItems)
}
.toolbar {
#if os(iOS)
EditButton()
#endif
Button(action: addItem) {
Label("Add Item", systemImage: "plus")
}
}
}
}
private func addItem() {
withAnimation {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
do {
try viewContext.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
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 {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
}
Core Data batch updates do not update the in-memory objects. You have to manually refresh afterwards.
Batch operations bypass the normal Core Data operations and operate directly on the underlying SQLite database (or whatever is backing your persistent store). They do this for benefits of speed but it means they also don't trigger all the stuff you get using normal fetch requests.
You need to do something like shown in Apple's Core Data Batch Programming Guide: Implementing Batch Updates - Updating Your Application After Execution
Original answer
do {
let fetch: NSFetchRequest<NSFetchRequestResult> = Item.fetchRequest()
let request = NSBatchDeleteRequest(fetchRequest: fetch)
request.resultType = .resultTypeObjectIDs
let result = try viewContext.execute(request) as? NSBatchDeleteResult
let objIDArray = result?.result as? [NSManagedObjectID]
let changes = [NSDeletedObjectsKey: objIDArray]
NSManagedObjectContext.mergeChanges(fromRemoteContextSave: changes, into: [viewContext])
} catch {
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
After completing a delete of a row in a SwiftUI List I am getting a "Thread 1: EXC_BAD_INSTRUCTION" error. It seems the Core Data delete works as after I restart that data has been removed. So maybe something to do with SwiftUI trying to update it's view after the Core Data delete is performed????
Code:
import SwiftUI
import CoreData
struct ContentView: View {
#Environment(\.managedObjectContext) var context
#FetchRequest(entity: GCItem.entity(), sortDescriptors: []) var gcItems: FetchedResults<GCItem>
private func addItem(title:String) {
let newItem = GCItem(context: context)
newItem.id = UUID()
newItem.title = title
do {
try context.save()
} catch let e as NSError {
fatalError("Unresolved error \(e), \(e.userInfo)")
}
}
private func deleteItem(at offsets:IndexSet) {
self.context.perform {
// Delete Item
for index in offsets {
let item = self.gcItems[index]
self.context.delete(item)
}
// Persist
do {
try self.context.save()
} catch let e as NSError {
// TODO: How to undelete list???
print("ERROR : Can not save GCItem items: \(e.description)")
}
}
}
var body: some View {
NavigationView {
VStack {
List() {
ForEach(gcItems) { gcItem in
HStack {
Text("test")
}
}
.onDelete(perform: self.deleteItem)
}
Button(action: { self.addItem(title: "Testing 123") }) {
Text("ADD ITEM")
}
}
}
}
}
#if DEBUG
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return ContentView().environment(\.managedObjectContext, context)
}
}
#endif
Screen Shot
The fix was NOT to use attributes in Core Data named "id". So I changed this to "myId" and then things worked fine.
Preview canvas is is crashing but in simulator everything working fine. I assuming it related to #ObservedObject and #Fetchrequest...
tried solution for here Previewing ContentView with CoreData
doesn't work
import SwiftUI
import CoreData
struct TemplateEditor: View {
#Environment(\.managedObjectContext) var managedObjectContext
#FetchRequest(
entity: GlobalPlaceholders.entity(),
sortDescriptors: [
NSSortDescriptor(keyPath: \GlobalPlaceholders.category, ascending: false),
]
) var placeholders: FetchedResults<GlobalPlaceholders>
#ObservedObject var documentTemplate: Templates
#State private var documentTemplateDraft = DocumentTemplateDraft()
#Binding var editing: Bool
var body: some View {
VStack(){
HStack(){
cancelButton
Spacer()
saveButton
}.padding()
addButton
ForEach(placeholders) {placeholder in
Text(placeholder.name)
}
TextField("Title", text: $documentTemplateDraft.title)
TextField("Body", text: $documentTemplateDraft.body)
.padding()
.frame(width: 100, height:400)
Spacer()
}
...
}
struct TemplateEditor_Previews: PreviewProvider {
static var previews: some View {
let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Templates")
request.sortDescriptors = [NSSortDescriptor(keyPath: \Templates.created, ascending: false)]
let documentTemplate = try! managedObjectContext.fetch(request).first as! Templates
return TemplateEditor(documentTemplate: documentTemplate, editing: .constant(true)).environment(\.managedObjectContext, managedObjectContext).environmentObject(documentTemplate)
}
}
Expected to generate preview
I'm not sure if your try line will work if there is no data.
let documentTemplate = try! managedObjectContext.fetch(request).first as! Templates
To get mine to work I created a test Item to use. Like this:
struct DetailView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
//Test data
let newEvent = Event.init(context: context)
newEvent.timestamp = Date()
return DetailView(event: newEvent).environment(\.managedObjectContext, context)
}
}
I've also noticed that I needed the .environment(.managedObjectContext, context) code in an earlier tabView that hosted the CoreData views or the preview would fail.
This answer seems to work in my recent project by replacing the default ContentView_Previews struct, though others are questioning whether it pulls persistent data. Credit goes to #ShadowDES - in the Master/Detail template project in Xcode Beta 7
I'm able to CRUD anything using Canvas (XCode Version 11.3 (11C29)) and it seems to run flawlessly.
#if DEBUG
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return ContentView().environment(\.managedObjectContext, context)
}
}
#endif
What works for me:
I create all of my sample data in the preview property of my persistence controller, building off of the template generated by Xcode when starting a project with the following settings: Interface - SwiftUI, Lifecycle - SwiftUI App, Use Core Data, Host in CloudKit. I have posted the template here:
import CoreData
struct PersistenceController {
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
// ** Prepare all sample data for previews here ** //
for _ in 0..<10 {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
}
do {
try viewContext.save()
} catch {
// handle error for production
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
return result
}()
let container: NSPersistentCloudKitContainer
init(inMemory: Bool = false) {
container = NSPersistentCloudKitContainer(name: "SwiftUISwiftAppCoreDataCloudKit")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// handle error for production
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
}
In my preview, I inject the persistence controller into the preview environment and for my view argument I use the registeredObjects.first(where:) method on the preview viewContext to pull the first object of the desired type:
struct MyView_Previews: PreviewProvider {
static var previews: some View {
MyView(item: PersistenceController.preview.container.viewContext.registeredObjects.first(where: { $0 is Item }) as! Item)
.environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
Edited 11/15/21
Persistence
import CoreData
struct PersistenceController {
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
Seed().prepareData(for: viewContext)
return result
}()
let container: NSPersistentCloudKitContainer
init(inMemory: Bool = false) {
container = NSPersistentCloudKitContainer(name: "SwiftUISwiftAppCoreDataCloudKit")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// handle error for production
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
}
struct Seed {
func prepareData(for viewContext: NSManagedObjectContext) {
// ** Prepare all sample data for previews here ** //
for _ in 0..<10 {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
}
do {
try viewContext.save()
} catch {
// handle error for production
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
Item Preview
struct ItemView_Previews: PreviewProvider {
static let persistence = PersistenceController.preview
static var item: Item = {
let context = persistence.container.viewContext
let item = Item(context: context)
item.timestamp = Date()
return item
}()
static var previews: some View {
ItemView(item: item)
.environment(\.managedObjectContext, persistence.container.viewContext)
}
}
So, if you put some code in an onAppear handler in the preview, it will run on boot. It even live updates as you type!
struct TemplateEditor_Previews: PreviewProvider {
static var previews: some View {
TemplateEditor().environment(\.managedObjectContext, AppDelegate.viewContext).onAppear {
let entity = GlobalPlaceholders(context: AppDelegate.viewContext)
entity.name = "abc123"
// Or create more, if you need more example data
try! AppDelegate.viewContext.save()
}
}
}
Note that I've wrapped up my viewContext in a static method on AppDelegate to make access a tiny bit less verbose and easier to remember:
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
static var persistentContainer: NSPersistentContainer {
return (UIApplication.shared.delegate as! AppDelegate).persistentContainer
}
static var viewContext: NSManagedObjectContext {
return persistentContainer.viewContext
}
Works for SwiftUI 2 app using the App template
I also had the previews crash and none of the other solutions were suitable or worked for me.
What I did was rather than the following:
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
return ContentView()
.environment(
\.managedObjectContext,
CoreDataManager.context
)
}
}
I fixed it with:
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = CoreDataManager.context
/* Optional sample data can be inserted here */
return ContentView()
.environment(
\.managedObjectContext,
context
)
}
}
Where CoreDataManager is:
enum CoreDataManager {
static var context: NSManagedObjectContext {
persistentContainer.viewContext
}
static let persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "MyContainerName")
container.loadPersistentStores { description, error in
guard let error = error else { return }
fatalError("Core Data error: '\(error.localizedDescription)'.")
}
return container
}()
}
Not exactly sure why this helped, but now it works perfectly. Additionally you can add sample data to this context where I have marked with a comment.
This is my solution.
I don't want use CoreData in view. I want MVVM style.
So you need to mock Core data for display in Canvas view.
This is an example :
// View
struct MyView: View {
#ObservedObject var viewModel: PreviewViewModel
}
// View Model
final class MyViewModel: ObservableObject {
#Published var repository: RepositoryProtocol // CoreData
}
// Repository
protocol RepositoryProtocol { }
class Repository: RepositoryProtocol { ... }
class MockRepository: RepositoryProtocol { ... } // Create a Mock
// Init of your view
// If Canvas use mock
if ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1" {
repository = MockRepository()
// else App use Repository
} else {
repository = Repository.shared
}
let viewModel = MyViewModel(repository:repository)
MyViewModel(viewModel: viewModel)
This worked for me. In the AppDelegate create a different preview context and fill it with objects.
lazy var persistentContainerPreview: NSPersistentContainer = {
let persistentContainer = NSPersistentContainer(name: "MyModel")
persistentContainer.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
}
})
let didCreateSampleData = UserDefaults.standard.bool(forKey: "didCreateSampleData")
if !didCreateSampleData {
let context = persistentContainer.viewContext
let recipe = Recipe(context: context)
recipe.title = "Soup 2"
recipe.difficultyName = "NOT TOO TRICKY"
recipe.difficultyValue = 1
recipe.heroImage = "dsfsdf"
recipe.ingredients = "meat"
recipe.method = "sdcsdsd"
recipe.published = Date()
recipe.recipeId = 1
recipe.servings = 4
recipe.tags = "sdfs"
recipe.totalTime = 100
recipe.totalTimeFormatted = "Less than 2 hours"
try! context.save()
}
return persistentContainer
}()
Then in your preview.
struct RecipeView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainerPreview.viewContext
let recipe = try! context.fetch(Recipe.fetchRequest()).first as! Recipe
RecipeView(recipe: recipe).environment(\.managedObjectContext, context)
}
}
One option is to NOT use Core Data in previews. This is helpful enough to see the UI of what I'm building but I'll still need to use Simulator to test the functionality.
#if !DEBUG
// Core Data related code e.g. #FetchRequest
#endif
What was suggested in Previewing ContentView with CoreData worked for me, Xcode Version 11.0 (11A419c) Mac OS 10.15 Beta (19A558d). My crash logs showed an index error,
*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty NSArray'
because there was no data there, so I had to handle this unique "preview" case and that got things working.
It crashes because it was instructed so in the PersistenceController:
struct PersistenceController {
...
static var preview: PersistenceController = {
...
do {
try viewContext.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
return result
}()
...
}
So the actual reason can be seen in the crash report. Actually, XCode 12.4 shows a warning about checking the crash report; however, the report is too verbose for a newbie like me from web development. Thus it took me a while to find out the problem, so I hope this would save some time for others.
...and the problem in my case was a required attribute was not set while populating the core data model for previews.
The thing is you need to find out which line cause the crash.
Since the canvas doesn't show the detailed error, using OSLog and Console.app to debug would be a possible solution.
For example:
import os.log
struct YourView_Previews: PreviewProvider {
static var previews: some View {
os_log("[DEBUG]-\(#function)---1--")
let moc = PersistenceController.preview.container.viewContext
os_log("[DEBUG]-\(#function)---2--")
let item = Item.previewData(context: moc)
os_log("[DEBUG]-\(#function)---3--")
return YourView(item: item, now: Date())
.environment(\.managedObjectContext, moc)
}
}
Remember to use filter to better catch the debug message from Console.
After finding out which line cause the crash, you can further look into the line and continue the process until you find the culprit.
(In my case, I forgot to add UUID to the preview data which causing the canvas to crash.)