将选中/未检查的任务保存到UserDefaults

//
//  ListViewModel.swift
import Foundation
class ListViewModel: ObservableObject {
    @Published var items: [ItemModel] = [] {
        didSet {
            saveItems()
    let itemsKey: String = "task_items_list"
    init() {
        myTaskItems()
    func myTaskItems() {
        let taskItems = [
            ItemModel(title: "This is the first task!", isCompleted: false),
            ItemModel(title: "This is the second task!", isCompleted: false),
            ItemModel(title: "This is the third task!", isCompleted: false),
            ItemModel(title: "This is the fourth task!", isCompleted: false),
            ItemModel(title: "This is the fifth task!", isCompleted: false)
        items.append(contentsOf: taskItems)
        guard
            let data = UserDefaults.standard.data(forKey: itemsKey),
            let savedTaskItems = try? JSONDecoder().decode([ItemModel].self, from: data)
        else { return }
        self.items = savedTaskItems
    // Update TaskdItems Toggle
    func updateItem(item:ItemModel) {
        if let index = items.firstIndex(where: { $0.id == item.id }) {
            items[index] = item.updateCompletion()
    // Save to UserDefaults
    func saveItems() {
        if let encodedData = try? JSONEncoder().encode(items) {
            UserDefaults.standard.set(encodedData, forKey: itemsKey)
}

//  ItemModel.swift
import Foundation
struct ItemModel:Identifiable, Codable {
    let id: String
    let title: String
    let isCompleted: Bool
    init(id: String = UUID().uuidString, title: String, isCompleted: Bool) {
        self.id = UUID().uuidString
        self.title = title
        self.isCompleted = isCompleted
    func updateCompletion() -> ItemModel {
        return ItemModel(id: id, title: title, isCompleted: !isCompleted)
}

//
//  ListView.swift
import SwiftUI
struct ListView: View {
    @EnvironmentObject var listViewModel: ListViewModel
    var body: some View {
        List {
            ForEach(listViewModel.items) { item in
                ListRowView(item: item)
                    .onTapGesture {
                        listViewModel.updateItem(item: item)
        .listStyle(PlainListStyle())
        .navigationTitle("My Task List")
    struct ListView_Previews: PreviewProvider {
        static var previews: some View {
            NavigationView {
                ListView()
            .environmentObject(ListViewModel())
}

//
//  ListRowView.swift
import SwiftUI
struct ListRowView: View {
    let item: ItemModel
    var body: some View {
        HStack {
            Image(systemName: item.isCompleted ? "checkmark.circle" : "circle")
                .foregroundColor(item.isCompleted ? .green : .gray)
            Text(item.title)
            Spacer()
        .font(.title2)
        .padding(.vertical, 8)
struct ListRowView_Previews: PreviewProvider {
    static var item1 = ItemModel(title: "First item!", isCompleted: false)
    static var item2 = ItemModel(title: "Second item!", isCompleted: true)
    static var previews: some View {
        Group {
            ListRowView(item: item1)
            ListRowView(item: item2)
        .previewLayout(.sizeThatFits)
}

//
//  TaskListApp.swift
import SwiftUI
@main
struct TaskListApp: App {
    @StateObject var listViewModel: ListViewModel = ListViewModel()
    var body: some Scene {
        WindowGroup {
            NavigationView {
                ListView()
            .environmentObject(listViewModel)
}

func myTaskItems() {        
    guard
        let data = UserDefaults.standard.data(forKey: itemsKey),
        let savedTaskItems = try? JSONDecoder().decode([ItemModel].self, from: data)
    else {
        let taskItems = [
            ItemModel(title: "This is the first task!", isCompleted: false),
            ItemModel(title: "This is the second task!", isCompleted: false),
            ItemModel(title: "This is the third task!", isCompleted: false),
            ItemModel(title: "This is the fourth task!", isCompleted: false),
            ItemModel(title: "This is the fifth task!", isCompleted: false)
        items.append(contentsOf: taskItems)
        return
    }

//needed to use array in @Appstorage
extension Array: RawRepresentable where Element: Codable{
    public init?(rawValue: String) {
            guard let data = rawValue.data(using: .utf8),
                  let result = try? JSONDecoder().decode([Element].self, from: data)
            else {
                return nil
            self = result
        public var rawValue: String {
            guard let data = try? JSONEncoder().encode(self),
                  let result = String(data: data, encoding: .utf8)
            else {
                return ""
            return result
class ListViewModel: ObservableObject {
    // this loads and saves the items automatic to UserDefaults
    @AppStorage("task_items_list") var items: [ItemModel] = []
    init() {
        //fill the collection only if it is empty
        if items.isEmpty{
            myTaskItems()
    func myTaskItems() {
        items = [
            ItemModel(title: "This is the first task!", isCompleted: false),
            ItemModel(title: "This is the second task!", isCompleted: false),
            ItemModel(title: "This is the third task!", isCompleted: false),
            ItemModel(title: "This is the fourth task!", isCompleted: false),
            ItemModel(title: "This is the fifth task!", isCompleted: false)
    //The rest of the functions are not needed
struct ItemModel: Identifiable, Codable {
    var id: String = UUID().uuidString
    var title: String
    var isCompleted: Bool
struct ListView: View {
    @EnvironmentObject var listViewModel: ListViewModel
    var body: some View {
        List {
            //Use the $ syntax to pass a binding on to the subviews
            ForEach($listViewModel.items) { $item in
                ListRowView(item: $item)
        .listStyle(PlainListStyle())
        .navigationTitle("My Task List")
struct ListRowView: View {
    //this binding will assure changes will bubble up into the viewmodel and will be saved in UserDefaults
    @Binding var item: ItemModel
    var body: some View {
        HStack {
            Image(systemName: item.isCompleted ? "checkmark.circle" : "circle")
                .foregroundColor(item.isCompleted ? .green : .gray)
            Text(item.title)
            Spacer()
        .font(.title2)
        .padding(.vertical, 8)

将选中/未检查的任务保存到UserDefaults

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