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")
]
}

”’