How would I get persistent data working in my reminder app - ios

Question

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")
]
}

Answer 1

The reason you are struggeling here is because you try to have multiple Source of truth.
documentation on dataflow in SwiftUI
You should move the code from HomeViewModel to your ReminderStore and change the static functions to instance functions. This would keep your logic in one place.
You can pass your ReminderStore to your HomeView as an #EnvironmentObject
This would simplify your code to:
class ReminderStore: ObservableObject {
#Published var reminds: [Reminder] = []
#Published var newRemindData = Reminder.Data()
private func fileURL() throws -> URL {
try FileManager.default.url(for: .documentDirectory,
in: .userDomainMask,
appropriateFor: nil,
create: false)
.appendingPathComponent("reminds.data")
}
func load() {
DispatchQueue.global(qos: .background).async {
do {
let fileURL = try self.fileURL()
guard let file = try? FileHandle(forReadingFrom: fileURL) else {
return
}
let reminds = try JSONDecoder().decode([Reminder].self, from: file.availableData)
DispatchQueue.main.async {
self.reminds = reminds
}
} catch {
DispatchQueue.main.async {
fatalError(error.localizedDescription)
}
}
}
}
func save() {
do {
let data = try JSONEncoder().encode(reminds)
let outfile = try fileURL()
try data.write(to: outfile)
} catch {
fatalError(error.localizedDescription)
}
}
func addRemindData() {
let newRemind = Reminder(data: newRemindData)
reminds.append(newRemind)
newRemindData = Reminder.Data()
}
}
struct RemindersApp: App {
#StateObject private var store = ReminderStore()
var body: some Scene {
WindowGroup {
NavigationView {
HomeView() {
store.save()
}
.navigationBarHidden(true)
.environmentObject(store)
}
.onAppear {
store.load()
}
}
}
}
struct HomeView: View {
#Environment(\.scenePhase) private var scenePhase
#EnvironmentObject private var store: ReminderStore
#State var addView = false
let saveAction: ()->Void
var body: some View {
VStack {
List {
ForEach(store.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: $store.newRemindData.title)
}
}
.toolbar {
ToolbarItem(placement: .cancellationAction) {
Button("Dismiss") {
store.newRemindData = Reminder.Data()
addView.toggle()
}
}
ToolbarItem(placement: .principal) {
Text("New Reminder")
.font(.title3)
}
ToolbarItem(placement: .confirmationAction) {
Button("Add") {
store.addRemindData()
addView.toggle()
}
}
}
}
}
.onChange(of: scenePhase) { phase in
if phase == .inactive { saveAction() }
}
}
}
}
}
An issue I would recommend solving:
Naming a type after something that´s allready taken by Swift is a bad idea. You should rename your Data struct to something different.

Answer 2

ReminderStore.save isn't invoking in time.
By the time it invokes it doesn't have/get the reminder data.
That's the first thing I would make sure gets done. You may end up running into other issues afterward, but I would personally focus on that first.