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Trouble implementing UserDefaults
(1 answer)
Attempt to insert non-property list object when trying to save a custom object in Swift 3
(6 answers)
Closed 5 months ago.
I am trying to save a simple struct in UserDefaults, but I get an error:
Terminating app due to uncaught exception
'NSInvalidArgumentException', reason: 'Attempt to insert non-property
list object...
Here is the struct:
struct saveStruct : Identifiable, Equatable {
var id = UUID()
var label : String
}
Here is the class that will save the struct:
class Game : ObservableObject {
#Published var structArray : [saveStruct]
let key = "structKey"
let defaults = UserDefaults.standard
init(){
structArray = defaults.object(forKey: key) as? [saveStruct] ?? []
}
func saveStructs() {
structArray.append(saveStruct(label: "newStruct"))
defaults.set(structArray, forKey: key)
}
}
And here's the view:
struct view : View {
#StateObject var game = Game()
var body : some View {
ZStack{
Button{
game.saveStructs()
} label: {
Text("Add to and Save structs")
}
}
}
}
I'd greatly appreciate any ideas on how to get around this. Thank you!
Related
clueless beginner here. Apologies if my question is formed poorly. This is the first time I ask a question of this scale and I have a hard time balancing between posting too much code for the good samaritans to read and too little to post an effective question. Huge thanks in advance!
I am trying to incorporate the textfieldalert in this post in my learner project. There are two Swift files in questions: File A (PosTextFieldAlertView) has an extension that needs to use two functions in File B (ListView).
These are the functions I need to use in File A.
func addPositive(){
let newPositive = PositiveEntity(context: viewContext)
newPositive.title = alertInput
save()
}
func save() {
do { try viewContext.save() } catch { print(error) }
}
I thought of/researched two methods: 1) duplicate the function in File A or 2) create instance of the view in File B that contains that functions according this post. However I ran into problems in both methods.
Duplicating the functions:
I copied the CoreData related properties in the PosTextFieldAlert struct. But now PosTextFieldAlert in the return part of the extension has the error of "Missing arguments for parameters [Core Data properties] in call". I don’t know how to set the property in the extension without referring or creating a different sets of Core Data entities.
Creating an instance of the relevant view
In the instance creation I would need to input the arguments but I don’t know how to refer to the same NSManagedObjectContext.
Code excerpts:
PosTextFieldAlertView
struct PosTextFieldAlert<Presenting>: View where Presenting: View {
var viewContext: NSManagedObjectContext
var positives: [PositiveEntity]
var targets: [TargetEntity]
#State private var alertInput = ""
// let listView = ListView(viewContext: NSManagedObjectContext, positives: PositiveEntity, negatives: NegativeEntity, targets: TargetEntity)
#Binding var isShowing: Bool
#Binding var text: String
let presenting: Presenting
let title: String
var body: some View {
GeometryReader { (deviceSize: GeometryProxy) in
ZStack {
self.presenting
.disabled(isShowing)
VStack {
Text(self.title)
TextField(self.title, text: self.$text)
Divider()
VStack{
HStack {
Button(action: {
withAnimation {
self.isShowing.toggle()
}
}) {
Text("+")
}.padding()
Button(action: {
withAnimation {
self.isShowing.toggle()
}
}) {
Text("-")
}.padding()
}
Button(action: {
withAnimation {
self.isShowing.toggle()
}
}) {
Text("Done")
}
}
}
.padding()
.background(Color.white)
.frame(
width: deviceSize.size.width*0.7,
height: deviceSize.size.height*0.7
)
.shadow(radius: 1)
.opacity(self.isShowing ? 1 : 0)
}
}
}
func addPositive(){
let newPositive = PositiveEntity(context: viewContext)
newPositive.title = alertInput
save()
}
func save() {
do { try viewContext.save() } catch { print(error) }
}
}
extension View {
func posTextFieldAlert(isShowing: Binding<Bool>,
text: Binding<String>,
title: String) -> some View {
PosTextFieldAlert(isShowing: isShowing,
text: text,
presenting: self,
title: title)
}
}
The code in ListView
struct ListView: View {
var viewContext: NSManagedObjectContext
var positives: [PositiveEntity]
var negatives: [NegativeEntity]
var targets: [TargetEntity]
//[layout of the project]
}
The Fetchrequests in ContentView:
#Environment(\.managedObjectContext) var viewContext
#FetchRequest(sortDescriptors: []) var targets: FetchedResults<TargetEntity>
#FetchRequest(sortDescriptors: []) var positives: FetchedResults<PositiveEntity>
#FetchRequest(sortDescriptors: []) var negatives: FetchedResults<NegativeEntity>
My app is meant to have a bunch of workouts in core data, each with a relationship to many exercises. A view should display the data in each workout (name, description etc.) and then iterate and display each exercise belonging to that workout.
Adding exercises and displaying them works fine. If an exercise is deleted, however it:
deletes from coredata no worries
the information seems to delete from iterableExercises
however, the Text line does not disappear. it goes from, for example "Squat, Description" to simply " , "
If I close the app entirely and reopen, then the " , " lines do completely disappear.
The problem code:
if let iterableExercises = workout.exercises?.array as? [ExerciseEntity] {
ForEach(iterableExercises) {exercise in
Text("\(exercise.name ?? ""), \(exercise.desc ?? "")")
}
}
I've got the entity relationship set as ordered, but I've also tried unordered with .allObjects instead of .array. This clearly isn't the problem as it's the array iterableExercises that's not correctly being reset?
EDIT: to reproduce, here's all the code you need and some screenshots of the CoreData model.
import SwiftUI
import CoreData
class ViewModel: ObservableObject {
let container: NSPersistentCloudKitContainer
#Published var savedWorkouts: [WorkoutEntity] = []
#Published var savedExercises: [ExerciseEntity] = []
// MARK: INIT
init() {
container = NSPersistentCloudKitContainer(name: "mre")
container.loadPersistentStores { description, error in
if let error = error {
print("Error loading CoreData: \(error)")
}
}
fetchWorkoutEntities()
fetchExerciseEntities()
}
// MARK: FETCHERS
func fetchWorkoutEntities() {
let request = NSFetchRequest<WorkoutEntity>(entityName: "WorkoutEntity")
do {
savedWorkouts = try container.viewContext.fetch(request)
} catch let error {
print("Error fetching WorkoutEntity: \(error)")
}
}
func fetchExerciseEntities() {
let request = NSFetchRequest<ExerciseEntity>(entityName: "ExerciseEntity")
do {
savedExercises = try container.viewContext.fetch(request)
} catch let error {
print("Error fetching ExerciseEntity: \(error)")
}
}
// MARK: SAVE
func saveData() {
do {
try container.viewContext.save()
fetchWorkoutEntities()
fetchExerciseEntities()
} catch let error {
print("Error saving: \(error)")
}
}
// MARK: ADDERS
func addWorkout(name: String) {
let _ = WorkoutEntity(context: container.viewContext)
saveData()
}
func addExerciseToWorkout(workout: WorkoutEntity, name: String) {
let newExercise = ExerciseEntity(context: container.viewContext)
newExercise.name = name
workout.addToExercises(newExercise)
saveData()
}
// MARK: DELETERS
func deleteWorkout(workout: WorkoutEntity) {
container.viewContext.delete(workout)
saveData()
}
func deleteExercise(exercise: ExerciseEntity) {
container.viewContext.delete(exercise)
saveData()
}
// MARK: TODO: UPDATERS
}
struct ContentView: View {
#StateObject var data = ViewModel()
var body: some View {
VStack {
Button {
data.addWorkout(name: "workout")
data.addExerciseToWorkout(workout: data.savedWorkouts[0], name: "[exercisename]")
} label: {
Text("Click ONCE to add workout to work with")
}
Spacer()
if let iterableExercises = data.savedWorkouts[0].exercises?.array as? [ExerciseEntity] {
ForEach(iterableExercises) { exercise in
Button {
data.deleteExercise(exercise: exercise)
} label: {
Text("Click to delete \(exercise.name ?? "") AFTER DELETING IF THIS STILL SHOWS BUT DOESN'T SHOW THE EXERCISE NAME THEN IT'S BROKEN")
}
}
}
Spacer()
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
screenshots of model
I’m not sure if this is the ONLY solution as #malhal gave quite an extensive and seemingly useful response.
But I came across a much easier and immediate fix, within my original solution. The inverse relationships must be specified. Doing this resolved all issues.
We don't use view model objects in SwiftUI. You need to learn the View struct and property wrappers which gives the consistency and efficiency of value types with the benefits of reference types. The property wrapper for core data is #FetchRequest which invalidates the View when the results change. It's also a DynamicProperty (which is how it gets the context from the environment) that you can use it directly without the property wrapper syntax which allows you to use a param in a predicate, in your case to do fetch the one-to-many relation, e.g.
struct WorkoutView: View {
private var fetchRequest: FetchRequest<Exercise>
private var exercices: FetchedResults<Exercise> {
fetchRequest.wrappedValue
}
init(workout: Workout) {
let sortAscending = true
let sortDescriptors = [SortDescriptor(\Exercise.timestamp, order: sortAscending ? .forward : .reverse)]
fetchRequest = FetchRequest(sortDescriptors: sortDescriptors, predicate: NSPredicate(format: "workout = %#", workout), animation: .default)
}
var body: some View {
List(exercises) { exercise in
ExerciseView(exercise: exercise)
}
}
}
For creating the NSPersistentContainer check out the Xcode App template with Core Data checked. Looks like this:
#main
struct TestApp: App {
let persistenceController = PersistenceController.shared
var body: some Scene {
WindowGroup {
ContentView()
.environment(\.managedObjectContext, persistenceController.container.viewContext)
}
}
The reason it is not an #StateObject is we don't want to invalidate this body when it changes and we need it to be init for previewing which is a different singleton.
struct PersistenceController {
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
... see template
That other code in your view model class can be moved to NSManagedObject and NSManagedObjectContext extensions. Use the Editor menu to generate the NSManagedObject extension for the model, the files need tidying up though and make sure use extension is selected for the entity.
I'm building an app using SwiftUI / Combine and trying to do so in an MVVM pattern. I'm getting a little confused as to how best to expose certain properties and in particular, in relation to the Core Data implementation.
In the main app file, I have set up an environmnt object as follows (I'll come to why later):
struct Football_GuruApp: App {
let persistenceController = PersistenceController.shared
#StateObject var favouritePlayers = FavouritePlayersViewModel()
var body: some Scene {
WindowGroup {
ContentView()
.environment(\.managedObjectContext, persistenceController.container.viewContext)
.environmentObject(favouritePlayers)
}
}
}
The app has 3 main views:
ContentView: this contains a TabView with 2 subviews: FetchedResultsView() and FavouritesView()
FetchedResultsView: this contains a subview FetchedPlayers() which looks like this:
struct FetchedPlayersView: View {
#EnvironmentObject var fetchedResultsVM: FetchedResultsViewModel
var body: some View {
Section(header: Text("Players")) {
ForEach(fetchedResultsVM.fetchedPlayers, content: { player in
PlayerView(player: player)
})
if fetchedResultsVM.playersExpandable {
MoreResultsButton(action: fetchedResultsVM.getMorePlayers, buttonTitle: "More players")
}
}
}
}
And finally FavouritesView:
struct FavouritesView: View {
#EnvironmentObject var favouritePlayersVM: FavouritePlayersViewModel
var context = PersistenceController.shared.container.viewContext
var body: some View {
List {
ForEach(context.fetchAll(PlayerCD.self)) { player in
PlayerView(player: PlayerViewModel.mapFromCoreData(player: player))
}
}
}
}
Within the PlayerView() (subview of FetchedPlayersView) we have a button:
FavouritesButton(playerViewModel: player)
When tapped we set a property on the PlayerViewModel to true:
playerViewModel.favourite = true
And then a didSet method on PlayerViewModel triggers the player to be stored to core data:
var favourite = false {
didSet {
self.mapToCoreData()
}
}
func mapToCoreData() {
let storedPlayer = PlayerCD(context: context)
storedPlayer.id = self.id
storedPlayer.firstName = self.firstName
storedPlayer.secondName = self.secondName
try? PersistenceController.shared.container.viewContext.save()
favouritePlayersVM.updateFavourites()
}
We have the following env object on the PlayerViewModel
#EnvironmentObject var favouritePlayersVM: FavouritePlayersViewModel
Finally, FavouritePlayersViewModel looks like this:
class FavouritePlayersViewModel: ObservableObject {
#Published var players = [PlayerViewModel]()
func updateFavourites() {
let context = PersistenceController.shared.container.viewContext
let savedPlayers = context.fetchAll(PlayerCD.self)
self.players = [PlayersViewModel]()
savedPlayers.forEach {
players.append(PlayerViewModel.mapFromCoreData(player: $0))
}
}
}
So the idea is that when the button is tapped, we store to core data and then at the same time we update the players list on FavouritePlayersViewModel which should then update the FavouritesView with the latest players. However, clearly I am struggling with the implementation of the environment object. I had thought that by exposing this at the root of the app, I would be able to access everywhere, but I guess that as PlayerViewModel, for example, is not a direct descendent, I can't access (as I'm getting a crash).
Perhaps using the env object is not the best fit here, but I'm struggling to work out how best to have it so that I can update the FavouritesViewModel players list from the PlayerViewModel whilst using the same instance of this FavouritesViewModel to update the FavouritesView.
By the same token, I'm also not able to access the NSManagedObjectContext that I set as #Environment in the root file in the view models either which is why I'm using the singleton of the persistent container to store my core data, which is not what I really wanted to do.
I'm currently creating a News-Feed-Reader App with SwiftUI.
I'm fetching the feed-items and storing them in CoreData
I'd like to display the objects in a List containing NavigationLinks to a Detail View and automatically mark them as read when clicking on them.
I'm currently fetching the objects and putting them in a ObservableObject.
This is the ObservableObject class:
final class FeedItem: ObservableObject, Hashable {
static func == (lhs: FeedItem, rhs: FeedItem) -> Bool {
return lhs.item.pubDate == rhs.item.pubDate && lhs.item.articleUrl == rhs.item.articleUrl
}
func hash(into hasher: inout Hasher) {
hasher.combine(item.articleUrl)
}
let objectWillChange = PassthroughSubject<Void, Never>()
init(item: NewsItem) {
self.item = item
}
// NewsItem is the Managed Object
var item: NewsItem
var bookmarked: Bool {
set {
//This function fetches the Object and marks it as bookmarked
DatabaseManager().markAs(item: item, .read, newValue)
self.item.bookmarked = newValue
}
get {
self.item.bookmarked
}
}
var read: Bool {
set {
//This function fetches the Object and marks it as read
DatabaseManager().markAs(item: item, .read, newValue)
self.item.read = newValue
}
get {
self.item.read
}
}
}
In the moment Im creating an environment Object (EO) containing an array of all ObservableObjects
This EO is passed down to the list and whenever Im clicking on an item Im setting its read value to true thereby changing the Core Data Object.
This is the list:
#EnvironmentObject var feed: // THe array of ObservableObjects
List() {
ForEach(feed.items.indices, id:\.self) { i in
Button(action: {
self.feed.items[i].read = true
self.selectedItem = i
self.showDetail = true
}) {
ListFeedItem(item: self.$feed.items[i])
}
}
}
This method is quite slow. Whenever I'm opening the Detail View and going back a few seconds later the List-Item takes multiple seconds to refresh.
Any ideas on how I could improve this?
I'm trying to use TextField to change the data of an attribute of CoreData, and everything I've come up with hasn't been successful. There is a similar question (listed below), and I'm going to post the code from the correct answer to that to explain it.
struct ItemDetail: View {
#EnvironmentObject var itemStore: ItemStore
let idx: Int
var body: some View {
NavigationView {
Stepper(value: $itemStore.items[idx].inventory) {
Text("Inventory is \(self.itemStore.items[idx].inventory)")
}
// Here I would like to do this
// TextField("PlaceHolder", $itemStore.items[idx].name)
// That doesn't work... also tried
// TextField("PlaceHolder", $name) - where name is a #State String
// How can you then automaticlly assign the new value of #State name
// To $itemStore.items[idx].name?
.padding()
.navigationBarTitle(itemStore.items[idx].name)
}
}
}
Original Question:
SwiftUI #Binding doesn't refresh View
I now have it working.
struct ItemDetail: View {
#EnvironmentObject var itemStore: ItemStore
let idx: Int
// Added new #State variable
#State var name = ""
var body: some View {
NavigationView {
Stepper(value: $itemStore.items[idx].inventory) {
Text("Inventory is \(self.itemStore.items[idx].inventory)")
}
TextField("Placeholder", text: $name) {
// When the enter key is tapped, this runs.
self.itemStore.items[self.idx].name = self.name
}
.padding()
.navigationBarTitle(itemStore.items[idx].name)
}
}
}