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I have a reminder app that I am trying to implement persistent data in but whenever I close the app no data is saved. I know how to make it work with a normal MVC but I would like to get it working with the view model that I have.
I think I know what needs to change to fix the problem but I am not sure how to get to the solution. I am pretty sure that in the ReminderApp file under the NavigationView where it says HomeViewModel(reminds: store.reminds) I think that the store.reminds part needs to be binded to with a $ at the beginning but when I try doing that it doesn’t work and instead says that HomeViewModel reminds property expects Reminder instead of Binding.
ReminderStore loads and saves the reminders to a file with the reminders and HomeViewModel contains the reminders array and appends a reminder to the array when a user adds a new reminder.
If anyone knows how to get this working that would be great since I have been stuck on this. My minimal reproducable example code is below.
RemindersApp
”’
import SwiftUI
@main
struct RemindersApp: App {
@StateObject private var store = ReminderStore()
var body: some Scene {
WindowGroup {
NavigationView {
HomeView(homeVM: HomeViewModel(reminds: store.reminds)) {
ReminderStore.save(reminds: store.reminds) { result in
if case .failure(let error) = result {
fatalError(error.localizedDescription)
}
}
}
.navigationBarHidden(true)
}
.onAppear {
ReminderStore.load { result in
switch result {
case .failure(let error):
fatalError(error.localizedDescription)
case .success(let reminds):
store.reminds = reminds
}
}
}
}
}
}
”’
HomeView
”’
import SwiftUI
struct HomeView: View {
@StateObject var homeVM: HomeViewModel
@Environment(\.scenePhase) private var scenePhase
@State var addView = false
let saveAction: ()->Void
var body: some View {
VStack {
List {
ForEach($homeVM.reminds) { $remind in
Text(remind.title)
}
}
}
.safeAreaInset(edge: .top) {
HStack {
Text("Reminders")
.font(.title)
.padding()
Spacer()
Button(action: {
addView.toggle()
}) {
Image(systemName: "plus")
.padding()
.font(.title2)
}
.sheet(isPresented: $addView) {
NavigationView {
VStack {
Form {
TextField("Title", text: $homeVM.newRemindData.title)
}
}
.toolbar {
ToolbarItem(placement: .cancellationAction) {
Button("Dismiss") {
homeVM.newRemindData = Reminder.Data()
addView.toggle()
}
}
ToolbarItem(placement: .principal) {
Text("New Reminder")
.font(.title3)
}
ToolbarItem(placement: .confirmationAction) {
Button("Add") {
homeVM.addRemindData(remindData: homeVM.newRemindData)
addView.toggle()
}
}
}
}
}
.onChange(of: scenePhase) { phase in
if phase == .inactive { saveAction() }
}
}
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
HomeView(homeVM: HomeViewModel(reminds: Reminder.sampleReminders), saveAction: {})
}
}
”’
ReminderStore
”’
import Foundation
import SwiftUI
class ReminderStore: ObservableObject {
@Published var reminds: [Reminder] = []
private static func fileURL() throws -> URL {
try FileManager.default.url(for: .documentDirectory,
in: .userDomainMask,
appropriateFor: nil,
create: false)
.appendingPathComponent("reminds.data")
}
static func load(completion: @escaping (Result<[Reminder], Error>) -> Void) {
DispatchQueue.global(qos: .background).async {
do {
let fileURL = try fileURL()
guard let file = try? FileHandle(forReadingFrom: fileURL) else {
DispatchQueue.main.async {
completion(.success([]))
}
return
}
let reminds = try JSONDecoder().decode([Reminder].self, from: file.availableData)
DispatchQueue.main.async {
completion(.success(reminds))
}
} catch {
DispatchQueue.main.async {
completion(.failure(error))
}
}
}
}
static func save(reminds: [Reminder], completion: @escaping (Result<Int, Error>) -> Void) {
do {
let data = try JSONEncoder().encode(reminds)
let outfile = try fileURL()
try data.write(to: outfile)
DispatchQueue.main.async {
completion(.success(reminds.count))
}
} catch {
DispatchQueue.main.async {
completion(.failure(error))
}
}
}
}
”’
HomeViewModel
”’
import Foundation
class HomeViewModel: ObservableObject {
@Published var reminds: [Reminder]
@Published var newRemindData = Reminder.Data()
init(reminds: [Reminder]) {
self.reminds = reminds
}
func addRemindData(remindData: Reminder.Data) {
let newRemind = Reminder(data: remindData)
reminds.append(newRemind)
newRemindData = Reminder.Data()
}
}
”’
Reminder
”’
import Foundation
struct Reminder: Identifiable, Codable {
var title: String
let id: UUID
init(title: String, id: UUID = UUID()) {
self.title = title
self.id = id
}
}
extension Reminder {
struct Data {
var title: String = ""
var id: UUID = UUID()
}
var data: Data {
Data(title: title)
}
mutating func update(from data: Data) {
title = data.title
}
init(data: Data) {
title = data.title
id = UUID()
}
}
extension Reminder {
static var sampleReminders = [
Reminder(title: "Reminder1"),
Reminder(title: "Reminder2"),
Reminder(title: "Reminder3")
]
}
”’
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