SwiftUI sample_swiftui accessibilityelement

    struct UserCell: View {
        var user: User

        var body: some View {
            VStack {
                Image(user.image)
                Text(user.name)
                Button("Options", action: showOptions)
            }
            .accessibilityElement(children: .combine)
        }
    }

    struct Point: CustomStringConvertible {
        let x: Int, y: Int

        var description: String {
            return "(\(x), \(y))"
        }
    }

    let p = Point(x: 21, y: 30)
    let s = String(describing: p)
    print(s)
    // Prints "(21, 30)"

    struct Point: CustomDebugStringConvertible {
        let x: Int, y: Int

        var debugDescription: String {
            return "(\(x), \(y))"
        }
    }

    let p = Point(x: 21, y: 30)
    let s = String(reflecting: p)
    print(s)
    // Prints "(21, 30)"

    
    let numbers = [2, 3, 5, 7]
    var numbersIterator = numbers.makeIterator()

    while let num = numbersIterator.next() {
        print(num)
    }
    // Prints "2"
    // Prints "3"
    // Prints "5"
    // Prints "7"

        
    @main
    struct MyApp: App {
        var body: some Scene {
            WindowGroup {
                Text("Hello, world!")
            }
        }
    }



    @main
    struct Mail: App {
        var body: some Scene {
            WindowGroup {
                MailViewer()
            }
            Settings {
                SettingsView()
            }
        }
    }


    @main
    struct Mail: App {
        @StateObject private var model = MailModel()

        var body: some Scene {
            WindowGroup {
                MailViewer()
                    .environmentObject(model) // Passed through the environment.
            }
            Settings {
                SettingsView(model: model) // Passed as an observed object.
            }
        }
    }

    @main
    struct MyApp: App {
        var body: some Scene {
            WindowGroup {
                Text("Hello, world!")
            }
        }
    }




   enum MyEnum: Int {
       case a
       case b
       case c
   }
   struct MyView: View {
       @AppStorage("MyEnumValue") private var value = MyEnum.a
       var body: some View { ... }
   }


   enum MyEnum: String {
       case a
       case b
       case c
   }
   struct MyView: View {
       @AppStorage("MyEnumValue") private var value = MyEnum.a
       var body: some View { ... }
   }


    enum MyEnum: String {
        case a
        case b
        case c
    }
    struct MyView: View {
        @AppStorage("MyEnumValue") private var value: MyEnum?
        var body: some View { ... }
    }

    enum MyEnum: Int {
        case a
        case b
        case c
    }
    struct MyView: View {
        @AppStorage("MyEnumValue") private var value: MyEnum?
        var body: some View { ... }
    }
    

    AsyncImage(url: URL(string: "https://example.com/icon.png"))
        .frame(width: 200, height: 200)


    AsyncImage(url: URL(string: "https://example.com/icon.png")) { image in
        image.resizable()
    } placeholder: {
        ProgressView()
    }
    .frame(width: 50, height: 50)



    AsyncImage(url: URL(string: "https://example.com/icon.png")) { phase in
        if let image = phase.image {
            image // Displays the loaded image.
        } else if phase.error != nil {
            Color.red // Indicates an error.
        } else {
            Color.blue // Acts as a placeholder.
        }
    }


    AsyncImage(url: URL(string: "https://example.com/icon.png")) { image in
        image.resizable(resizingMode: .tile)
    } placeholder: {
        Color.green
    }

    
    AsyncImage(url: URL(string: "https://example.com/icon.png")) { phase in
        if let image = phase.image {
            image // Displays the loaded image.
        } else if phase.error != nil {
            Color.red // Indicates an error.
        } else {
            Color.blue // Acts as a placeholder.
        }
    }

    
    

    
    AsyncImage(url: URL(string: "https://example.com/icon.png")) { phase in
        if let image = phase.image {
            image // Displays the loaded image.
        } else if phase.error != nil {
            Color.red // Indicates an error.
        } else {
            Color.blue // Acts as a placeholder.
        }
    }


    let extraOptions = ShippingOptions(rawValue: 255)
    print(extraOptions.isStrictSuperset(of: .all))
    // Prints "true"

    


    

    struct Point: CustomStringConvertible {
        let x: Int, y: Int

        var description: String {
            return "(\(x), \(y))"
        }
    }

    let p = Point(x: 21, y: 30)
    let s = String(describing: p)
    print(s)
    // Prints "(21, 30)"

    

    struct PlayButton: View {
        @Binding var isPlaying: Bool

        var body: some View {
            Button(action: {
                self.isPlaying.toggle()
            }) {
                Image(systemName: isPlaying ? "pause.circle" : "play.circle")
            }
        }
    }


    struct PlayerView: View {
        var episode: Episode
        @State private var isPlaying: Bool = false

        var body: some View {
            VStack {
                Text(episode.title)
                Text(episode.showTitle)
                PlayButton(isPlaying: $isPlaying)
            }
        }
    }



    struct PlayButton: View {
        @Binding var isPlaying: Bool

        var body: some View {
            Button(action: {
                self.isPlaying.toggle()
            }) {
                Image(systemName: isPlaying ? "pause.circle" : "play.circle")
            }
        }
    }


    struct PlayerView: View {
        var episode: Episode
        @State private var isPlaying: Bool = false

        var body: some View {
            VStack {
                Text(episode.title)
                Text(episode.showTitle)
                PlayButton(isPlaying: $isPlaying)
            }
        }
    }
    
    let numbers = [10, 20, 30, 40, 50]
    if let index = numbers.firstIndex(of: 30) {
        print(numbers[index ..< numbers.endIndex])
    }
    // Prints "[30, 40, 50]"

    

    var c = MyFancyCollection([10, 20, 30, 40, 50])
    var i = c.startIndex
    while i != c.endIndex {
        c[i] /= 5
        i = c.index(after: i)
    }
    // c == MyFancyCollection([2, 4, 6, 8, 10])
    
    var streets = ["Adams", "Bryant", "Channing", "Douglas", "Evarts"]
    print(streets[1])
    // Prints "Bryant"

    

    Button(action: signIn) {
        Text("Sign In")
    }



    Button("Sign In", action: signIn)



    List {
        // Cells that show all the current folders.
        ForEach(folders) { folder in
            Text(folder.title)
        }

        // A cell that, when selected, adds a new folder.
        Button(action: addItem) {
            Label("Add Folder", systemImage: "folder.badge.plus")
        }
    }


    .contextMenu {
        Button("Cut", action: cut)
        Button("Copy", action: copy)
        Button("Paste", action: paste)
    }


     Button("Delete", role: .destructive, action: delete)



    HStack {
        Button("Sign In", action: signIn)
        Button("Register", action: register)
    }
    .buttonStyle(.bordered)



    

    
    struct RedBorderedButtonStyle: PrimitiveButtonStyle {
        func makeBody(configuration: Configuration) -> some View {
            Button(configuration)
                .border(Color.red)
        }
    }

    
    List {
        ForEach(items) { item in
            Text(item.title)
                .swipeActions {
                    Button(role: .destructive) { delete() } label: {
                        Label("Delete", systemImage: "trash")
                    }
                }
        }
    }
    .navigationTitle("Shopping List")

    
    struct MyButtonStyle: ButtonStyle {
        func makeBody(configuration: Configuration) -> some View {
            configuration.label
                .font(
                    configuration.role == .cancel ? .title2.bold() : .title2)
                .foregroundColor(
                    configuration.role == .destructive ? Color.red : nil)
        }
    }

You can create one of each button using this style to see the effect:

    VStack(spacing: 20) {
        Button("Cancel", role: .cancel) {}
        Button("Delete", role: .destructive) {}
        Button("Continue") {}
    }
    .buttonStyle(MyButtonStyle())

    

    Canvas { context, size in
        context.stroke(
            Path(ellipseIn: CGRect(origin: .zero, size: size)),
            with: .color(.green),
            lineWidth: 4)
    }
    .frame(width: 300, height: 200)
    .border(Color.blue)



    struct ScatterPlotView<Mark: View>: View {
        let rects: [CGRect]
        let mark: Mark

        enum SymbolID: Int {
            case mark
        }

        var body: some View {
            Canvas { context, size in
                if let mark = context.resolveSymbol(id: SymbolID.mark) {
                    for rect in rects {
                        context.draw(mark, in: rect)
                    }
                }
            } symbols: {
                mark.tag(SymbolID.mark)
            }
            .frame(width: 300, height: 200)
            .border(Color.blue)
        }
    }

    

    ScatterPlotView(rects: rects, mark: Image(systemName: "circle"))



    Canvas { context, size in
        context.stroke(
            Path(ellipseIn: CGRect(origin: .zero, size: size)),
            with: .color(.green),
            lineWidth: 4)
    }
    .frame(width: 300, height: 200)
    .border(Color.blue)

    
    
* Load a color from an Asset Catalog:
    ```
    let aqua = Color("aqua") // Looks in your app's main bundle by default.
    ```
* Specify component values, like red, green, and blue; hue,
  saturation, and brightness; or white level:
    ```
    let skyBlue = Color(red: 0.4627, green: 0.8392, blue: 1.0)
    let lemonYellow = Color(hue: 0.1639, saturation: 1, brightness: 1)
    let steelGray = Color(white: 0.4745)
    ```
* Create a color instance from another color, like a
  <doc://com.apple.documentation/documentation/UIKit/UIColor> or an
  <doc://com.apple.documentation/documentation/AppKit/NSColor>:
    ```
    #if os(iOS)
    let linkColor = Color(uiColor: .link)
    #elseif os(macOS)
    let linkColor = Color(nsColor: .linkColor)
    #endif
    ```
* Use one of a palette of predefined colors, like ``ShapeStyle/black``,
  ``ShapeStyle/green``, and ``ShapeStyle/purple``.


    Image(systemName: "leaf.fill")
        .foregroundStyle(Color.green)



    ZStack {
        skyBlue
        Image(systemName: "sun.max.fill")
            .foregroundStyle(lemonYellow)
    }
    .frame(width: 200, height: 100)


    Text("Accent Color")
        .foregroundStyle(Color.accentColor)

    
    struct Hello: View {
        var body: some View {
            ZStack {
                Color("background")
                Text("Hello, world!")
                    .foregroundStyle(Color("foreground"))
            }
            .frame(width: 200, height: 100)
        }
    }

    
    struct Box: View {
        var body: some View {
            Color(UIColor.link)
                .frame(width: 200, height: 100)
        }
    }

    
    struct Box: View {
        var body: some View {
            Color(uiColor: .link)
                .frame(width: 200, height: 100)
        }
    }

    
    struct FormattingControls: View {
        @State private var bgColor =
            Color(.sRGB, red: 0.98, green: 0.9, blue: 0.2)

        var body: some View {
            VStack {
                ColorPicker("Alignment Guides", selection: $bgColor)
            }
        }
    }



    final class Settings: ObservableObject {
        @Published var alignmentGuideColor =
            Color(.sRGB, red: 0.98, green: 0.9, blue: 0.2)
    }

    struct FormattingControls: View {
        @State private var settings = Settings()

        var body: some View {
            VStack {
                // Other formatting controls.
                ColorPicker("Alignment Guides",
                    selection: $settings.alignmentGuideColor
                )
            }
        }
    }

    
    func showColorPicker(_ title: String, color: Binding<Color>) {
        ColorPicker(title, selection: color)
    }

    

    

    let selectedSize = PaperSize.Letter
    print(selectedSize.rawValue)
    // Prints "Letter"

    print(selectedSize == PaperSize(rawValue: selectedSize.rawValue)!)
    // Prints "true"
    

    func selectHearts() {
        // Act on hearts selection.
    }
    func selectClubs() { ... }
    func selectSpades() { ... }
    func selectDiamonds() { ... }

    let menuItems = ContextMenu {
        Button("♥️ - Hearts", action: selectHearts)
        Button("♣️ - Clubs", action: selectClubs)
        Button("♠️ - Spades", action: selectSpades)
        Button("♦️ - Diamonds", action: selectDiamonds)
    }

    struct ContextMenuMenuItems: View {
        private var shouldShowMenu = true
        var body: some View {
            VStack {
                Text("Favorite Card Suit")
                    .padding()
                    .contextMenu(shouldShowMenu ? menuItems : nil)
            }
        }
    }


    struct RedBorderControlGroupStyle: ControlGroupStyle {
        func makeBody(configuration: Configuration) -> some View {
            ControlGroup(configuration)
                .border(Color.red)
        }
    }

    
    @State private var date = Date()

    var body: some View {
        DatePicker(
            "Start Date",
            selection: $date,
            displayedComponents: [.date]
        )
    }


    @State private var date = Date()
    let dateRange: ClosedRange<Date> = {
        let calendar = Calendar.current
        let startComponents = DateComponents(year: 2021, month: 1, day: 1)
        let endComponents = DateComponents(year: 2021, month: 12, day: 31, hour: 23, minute: 59, second: 59)
        return calendar.date(from:startComponents)!
            ...
            calendar.date(from:endComponents)!
    }()

    var body: some View {
        DatePicker(
            "Start Date",
             selection: $date,
             in: dateRange,
             displayedComponents: [.date, .hourAndMinute]
        )
    }


    @State private var date = Date()

    var body: some View {
        DatePicker(
            "Start Date",
            selection: $date,
            displayedComponents: [.date]
        )
        .datePickerStyle(.graphical)
    }


    

    let selectedSize = PaperSize.Letter
    print(selectedSize.rawValue)
    // Prints "Letter"

    print(selectedSize == PaperSize(rawValue: selectedSize.rawValue)!)
    // Prints "true"
    
    struct ToggleStates {
        var oneIsOn: Bool = false
        var twoIsOn: Bool = true
    }
    @State private var toggleStates = ToggleStates()
    @State private var topExpanded: Bool = true

    var body: some View {
        DisclosureGroup("Items", isExpanded: $topExpanded) {
            Toggle("Toggle 1", isOn: $toggleStates.oneIsOn)
            Toggle("Toggle 2", isOn: $toggleStates.twoIsOn)
            DisclosureGroup("Sub-items") {
                Text("Sub-item 1")
            }
        }
    }

    struct SheetView: View {
        @Environment(\.dismiss) var dismiss

        var body: some View {
            NavigationView {
                SheetContents()
                    .toolbar {
                        Button("Done") {
                            dismiss()
                        }
                    }
            }
        }
    }


    @main
    struct MyApp: App {
        var body: some Scene {
            DocumentGroup(newDocument: TextFile()) { file in
                ContentView(document: file.$document)
            }
        }
    }


    @main
    struct MyApp: App {
        var body: some Scene {
            DocumentGroup(viewing: MyImageFormatDocument.self) {
                MyImageFormatViewer(image: $0.document)
            }
        }
    }


    @main
    struct MyApp: App {
        var body: some Scene {
            DocumentGroup(newDocument: TextFile()) { group in
                ContentView(document: group.$document)
            }
            DocumentGroup(viewing: MyImageFormatDocument.self) { group in
                MyImageFormatViewer(image: group.document)
            }
        }
    }


    @main
    struct MyApp: App {
        var body: some Scene {
            DocumentGroup(newDocument: TextFile()) { file in
                ContentView(document: file.$document)
            }
        }
    }

    
    @main
    struct MyApp: App {
        var body: some Scene {
            DocumentGroup(viewing: MyImageFormatDocument.self) { file in
                MyImageFormatViewer(image: file.document)
            }
        }
    }

    

    struct DragGestureView: View {
        @State var isDragging = false

        var drag: some Gesture {
            DragGesture()
                .onChanged { _ in self.isDragging = true }
                .onEnded { _ in self.isDragging = false }
        }

        var body: some View {
            Circle()
                .fill(self.isDragging ? Color.red : Color.blue)
                .frame(width: 100, height: 100, alignment: .center)
                .gesture(drag)
        }
    }

    

    print(PaperSize(rawValue: "Legal"))
    // Prints "Optional("PaperSize.Legal")"

    print(PaperSize(rawValue: "Tabloid"))
    // Prints "nil"

    
    

    let selectedSize = PaperSize.Letter
    print(selectedSize.rawValue)
    // Prints "Letter"

    print(selectedSize == PaperSize(rawValue: selectedSize.rawValue)!)
    // Prints "true"
    
    @State private var fruits = [
        "Apple",
        "Banana",
        "Papaya",
        "Mango"
    ]

    var body: some View {
        NavigationView{
            List {
                ForEach(
                    fruits,
                    id: \.self
                ) { fruit in
                    Text(fruit)
                }
                .onDelete { self.deleteFruit(at :$0) }
                .onMove { self.moveFruit(from: $0, to: $1) }
            }
            .navigationTitle("Fruits")
            .toolbar { EditButton() }
        }
    }



    EllipticalGradient(
        gradient: .init(colors: [.blue, .green]),
        center: .topLeading,
        startRadiusFraction: 0,
        endRadiusFraction: 1)

    

    EllipticalGradient(
        colors: [.blue, .green],
        center: .topLeading,
        startRadiusFraction: 0,
        endRadiusFraction: 1)

    
    EllipticalGradient(
        stops: [
            .init(color: .blue, location: 0.0),
            .init(color: .green, location: 0.9),
            .init(color: .green, location: 1.0),
        ],
        center: .topLeading,
        startRadiusFraction: 0,
        endRadiusFraction: 1)

    

    struct EmphasizedLayout: ViewModifier {
        func body(content: Content) -> some View {
            content
                .background(Color.yellow)
                .border(Color.red)
        }
    }

    struct ContentView: View {
        var body: some View {
            Text("Hello, World!")
                .modifier(modifier)
        }

        var modifier: some ViewModifier {
            #if DEBUG
                return EmphasizedLayout()
            #else
                return EmptyModifier()
            #endif
        }
    }


    let progressView = ProgressView()
    print("\(type(of:progressView))")
    // Prints: ProgressView<EmptyView, EmptyView>


    @Environment(\.colorScheme) var colorScheme: ColorScheme


    if colorScheme == .dark { // Checks the wrapped value.
        DarkContent()
    } else {
        LightContent()
    }


    struct MyView: View {
        @Environment(\.colorScheme) var colorScheme: ColorScheme

        // ...
    }

    
    @Environment(\.colorScheme) var colorScheme: ColorScheme

    var body: some View {
        if colorScheme == .dark {
            DarkContent()
        } else {
            LightContent()
        }
    }

    
    private struct MyEnvironmentKey: EnvironmentKey {
        static let defaultValue: String = "Default value"
    }



    extension EnvironmentValues {
        var myCustomValue: String {
            get { self[MyEnvironmentKey.self] }
            set { self[MyEnvironmentKey.self] = newValue }
        }
    }


    MyView()
        .environment(\.myCustomValue, "Another string")


    extension View {
        func myCustomValue(_ myCustomValue: String) -> some View {
            environment(\.myCustomValue, myCustomValue)
        }
    }



    MyView()
        .myCustomValue("Another string")



    struct MyView: View {
        @Environment(\.myCustomValue) var customValue: String

        var body: some View {
            Text(customValue) // Displays "Another value".
        }
    }


    @Environment(\.locale) var locale: Locale



    MyView()
        .environment(\.lineLimit, 2)


    MyView()
        .lineLimit(2)



    MyView()
        .popover(isPresented: $isPopped) {
            PopoverContent()
                .preferredColorScheme(.dark)
        }


    private struct MyEnvironmentKey: EnvironmentKey {
        static let defaultValue: String = "Default value"
    }

    extension EnvironmentValues {
        var myCustomValue: String {
            get { self[MyEnvironmentKey.self] }
            set { self[MyEnvironmentKey.self] = newValue }
        }
    }

    extension View {
        func myCustomValue(_ myCustomValue: String) -> some View {
            environment(\.myCustomValue, myCustomValue)
        }
    }


    private struct MyEnvironmentKey: EnvironmentKey {
        static let defaultValue: String = "Default value"
    }

    extension EnvironmentValues {
        var myCustomValue: String {
            get { self[MyEnvironmentKey.self] }
            set { self[MyEnvironmentKey.self] = newValue }
        }
    }

    

    extension View {
        func myCustomValue(_ myCustomValue: String) -> some View {
            environment(\.myCustomValue, myCustomValue)
        }
    }

    
    HStack {
        Image(systemName: "heart")
        Image(systemName: "heart")
            .environment(\.symbolVariants, .none)
    }
    .symbolVariant(.fill)

    
    struct ContentView: View {
        @State var text = ""

        var body: some View {
            SearchReadingView()
                .searchable(text: $text)
        }
    }

    struct SearchReadingView: View {
        @Environment(\.isSearching) var isSearching

        var body: some View {
            if isSearching {
               Text("Searching!")
            } else {
                Text("Not searching.")
        }
    }

    

    NavigationView {
        MyList()
           .searchable(text: $text)
    }

    struct MyList: View {
        @State private var isPresented = false
        @Environment(\.isSearching) private var isSearching

        var body: some View {
            Text("Main List")
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .overlay {
                    if isSearching {
                        Button {
                            isPresented = true
                        } label: {
                            Text("Present")
                                .frame(
                                    maxWidth: .infinity,
                                    maxHeight: .infinity
                                )
                                .background()
                        }
                        .sheet(isPresented: $isPresented) {
                            NavigationView {
                                DetailView()
                            }
                        }
                    }
                }
        }
    }

    struct DetailView: View {
        @Environment(\.dismiss) private var dismiss
        @Environment(\.dismissSearch) private var dismissSearch

        var body: some View {
            Text("Detail Content")
                .toolbar {
                    Button("Add") {
                        dismiss()
                        dismissSearch()
                    }
                }
        }
    }
    

    Text("Visit [Example Co](https://www.example.com) for details.")
        .environment(\.openURL, OpenURLAction { url in
            handleURL(url)
            return .handled
        })

    

    private struct MyButtonStyle: ButtonStyle {
        @Environment(\.keyboardShortcut)
        private var shortcut: KeyboardShortcut?

        func makeBody(configuration: Configuration) -> some View {
            let labelFont = Font.body
                .weight(shortcut == .defaultAction ? .bold : .regular)
            configuration.label
                .font(labelFont)
        }
    }

    
    HStack {
        Text("This is a very long label:")
            .lineLimit(1)
            .minimumScaleFactor(0.5)
        TextField("My Long Text Field", text: $myTextField)
            .frame(width: 250, height: 50, alignment: .center)
    }

    
    let numbers = [2, 3, 5, 7]
    var numbersIterator = numbers.makeIterator()

    while let num = numbersIterator.next() {
        print(num)
    }
    // Prints "2"
    // Prints "3"
    // Prints "5"
    // Prints "7"

        

    @FetchRequest(sortDescriptors: [SortDescriptor(\.time, order: .reverse)])
    private var quakes: FetchedResults<Quake>


    @FetchRequest(fetchRequest: request)
    private var quakes: FetchedResults<Quake>


    ContentView()
        .environment(
            \.managedObjectContext,
            QuakesProvider.shared.container.viewContext)


    @FetchRequest(fetchRequest: request)
    private var quakes: FetchedResults<Quake>

    
    Text("Found \(quakes.count) earthquakes")

    
    var fetchRequest = FetchRequest<Quake>(fetchRequest: request)
    var quakes: FetchedResults<Quake> { fetchRequest.wrappedValue }

    
    @FetchRequest(sortDescriptors: [SortDescriptor(\.time, order: .reverse)])
    private var quakes: FetchedResults<Quake>

    

    Table(quakes, sortOrder: $quakes.sortDescriptors) {
        TableColumn("Place", value: \.place)
        TableColumn("Time", value: \.time) { quake in
            Text(quake.time, style: .time)
        }
    }

    
    @State private var query = ""

    
    .onChange(of: query) { value in
        quakes.nsPredicate = query.isEmpty
            ? nil
            : NSPredicate(format: "place CONTAINS %@", value)
    }

    
    TextField("Filter", text: $query)

    
    @FetchRequest(sortDescriptors: [SortDescriptor(\.time, order: .reverse)])
    private var quakes: FetchedResults<Quake>

    
    Table(quakes, sortOrder: $quakes.sortDescriptors) {
        TableColumn("Place", value: \.place)
        TableColumn("Time", value: \.time) { quake in
            Text(quake.time, style: .time)
        }
    }

    

    extension Quake {
        var request: NSFetchRequest<Quake> {
            let request = NSFetchRequest<Quake>(entityName: "Quake")
            request.sortDescriptors = [
                NSSortDescriptor(
                    keyPath: \Quake.time,
                    ascending: true)]
            request.fetchLimit = 1000
            return request
        }
    }

    

    @FetchRequest(fetchRequest: Quake.request)
    private var quakes: FetchedResults<Quake>

    

    @FetchRequest(sortDescriptors: [SortDescriptor(\.time, order: .reverse)])
    private var quakes: FetchedResults<Quake>



    List(quakes) { quake in
        NavigationLink(destination: QuakeDetail(quake: quake)) {
            QuakeRow(quake: quake)
        }
    }


    ContentView()
        .environment(
            \.managedObjectContext,
            QuakesProvider.shared.container.viewContext)


    struct LoginForm {
        enum Field: Hashable {
            case username
            case password
        }

        @State private var username = ""
        @State private var password = ""
        @FocusState private var focusedField: Field?

        var body: some View {
            Form {
                TextField("Username", text: $username)
                    .focused($focusedField, equals: .username)

                SecureField("Password", text: $password)
                    .focused($focusedField, equals: .password)

                Button("Sign In") {
                    if username.isEmpty {
                        focusedField = .username
                    } else if password.isEmpty {
                        focusedField = .password
                    } else {
                        handleLogin(username, password)
                    }
                }
            }
        }
    }


    struct ContentView: View {
        enum Field: Hashable {
            case name
            case fullName
        }
        @FocusState private var focusedField: Field?

        var body: some View {
            TextField("Full Name", ...)
                .focused($focusedField, equals: .name)
                .focused($focusedField, equals: .fullName)
        }
    }


    struct ContentView: View {
        enum Field: Hashable {
            case name
            case fullName
        }
        @FocusState private var focusedField: Field?

        var body: some View {
            TextField("Name", ...)
                .focused($focusedField, equals: .name)
            TextField("Full Name", ...)
                .focused($focusedField, equals: .name) // incorrect re-use of .name
        }
    }



    struct Sidebar: View {
        @State private var filterText = ""
        @FocusState private var isFiltering: Bool

        var body: some View {
            VStack {
                Button("Filter Sidebar Contents") {
                    isFiltering = true
                }

                TextField("Filter", text: $filterText)
                    .focused($isFiltering)
            }
        }
    }
    
    // Use native Core Text API to create desired ctFont.
    let ctFont = CTFontCreateUIFontForLanguage(.system, 12, nil)!

    // Create SwiftUI Text with the CTFont instance.
    let text = Text("Hello").font(Font(ctFont))
    
    private struct NamedFont: Identifiable {
        let name: String
        let font: Font
        var id: String { name }
    }

    private let namedFonts: [NamedFont] = [
        NamedFont(name: "Large Title", font: .largeTitle),
        NamedFont(name: "Title", font: .title),
        NamedFont(name: "Headline", font: .headline),
        NamedFont(name: "Body", font: .body),
        NamedFont(name: "Caption", font: .caption)
    ]

    var body: some View {
        ForEach(namedFonts) { namedFont in
            Text(namedFont.name)
                .font(namedFont.font)
        }
    }



    var body: some View {
        NavigationView {
            Form {
                Section(header: Text("Notifications")) {
                    Picker("Notify Me About", selection: $notifyMeAbout) {
                        Text("Direct Messages").tag(NotifyMeAboutType.directMessages)
                        Text("Mentions").tag(NotifyMeAboutType.mentions)
                        Text("Anything").tag(NotifyMeAboutType.anything)
                    }
                    Toggle("Play notification sounds", isOn: $playNotificationSounds)
                    Toggle("Send read receipts", isOn: $sendReadReceipts)
                }
                Section(header: Text("User Profiles")) {
                    Picker("Profile Image Size", selection: $profileImageSize) {
                        Text("Large").tag(ProfileImageSize.large)
                        Text("Medium").tag(ProfileImageSize.medium)
                        Text("Small").tag(ProfileImageSize.small)
                    }
                    Button("Clear Image Cache") {}
                }
            }
        }
    }


    var body: some View {
        Spacer()
        HStack {
            Spacer()
            Form {
                Picker("Notify Me About:", selection: $notifyMeAbout) {
                    Text("Direct Messages").tag(NotifyMeAboutType.directMessages)
                    Text("Mentions").tag(NotifyMeAboutType.mentions)
                    Text("Anything").tag(NotifyMeAboutType.anything)
                }
                Toggle("Play notification sounds", isOn: $playNotificationSounds)
                Toggle("Send read receipts", isOn: $sendReadReceipts)

                Picker("Profile Image Size:", selection: $profileImageSize) {
                    Text("Large").tag(ProfileImageSize.large)
                    Text("Medium").tag(ProfileImageSize.medium)
                    Text("Small").tag(ProfileImageSize.small)
                }
                .pickerStyle(.inline)

                Button("Clear Image Cache") {}
            }
            Spacer()
        }
        Spacer()
    }


    

    let selectedSize = PaperSize.Letter
    print(selectedSize.rawValue)
    // Prints "Letter"

    print(selectedSize == PaperSize(rawValue: selectedSize.rawValue)!)
    // Prints "true"
    
    struct SimpleLongPressGestureView: View {
        @GestureState var isDetectingLongPress = false

        var longPress: some Gesture {
            LongPressGesture(minimumDuration: 3)
                .updating($isDetectingLongPress) { currentState, gestureState, transaction in
                    gestureState = currentState
                }
        }

        var body: some View {
            Circle()
                .fill(self.isDetectingLongPress ? Color.red : Color.green)
                .frame(width: 100, height: 100, alignment: .center)
                .gesture(longPress)
        }
    }


    Canvas { context, size in
        context.fill(
            Path(ellipseIn: CGRect(origin: .zero, size: size)),
            with: .color(.green))
    }
    .frame(width: 300, height: 200)


    let halfSize = size.applying(CGAffineTransform(scaleX: 0.5, y: 0.5))
    context.clip(to: Path(CGRect(origin: .zero, size: halfSize)))
    context.fill(
        Path(ellipseIn: CGRect(origin: .zero, size: size)),
        with: .color(.green))


    // Create a copy of the context to draw a clipped ellipse.
    var maskedContext = context
    let halfSize = size.applying(CGAffineTransform(scaleX: 0.5, y: 0.5))
    maskedContext.clip(to: Path(CGRect(origin: .zero, size: halfSize)))
    maskedContext.fill(
        Path(ellipseIn: CGRect(origin: .zero, size: size)),
        with: .color(.green))

    // Go back to the original context to draw the rectangle.
    let origin = CGPoint(x: size.width / 4, y: size.height / 4)
    context.fill(
        Path(CGRect(origin: origin, size: halfSize)),
        with: .color(.blue))


    enum PaperSize: String {
        case A4, A5, Letter, Legal
    }

    print(PaperSize(rawValue: "Legal"))
    // Prints "Optional("PaperSize.Legal")"

    print(PaperSize(rawValue: "Tabloid"))
    // Prints "nil"

        
        
        
        
    Group {
        Text("SwiftUI")
        Text("Combine")
        Text("Swift System")
    }
    .font(.headline)


    Group {
        if isLoggedIn {
            WelcomeView()
        } else {
            LoginView()
        }
    }
    .navigationBarTitle("Start")


    var body: some View {
        VStack {
            Group {
                Text("1")
                Text("2")
                Text("3")
                Text("4")
                Text("5")
                Text("6")
                Text("7")
                Text("8")
                Text("9")
                Text("10")
            }
            Text("11")
        }
    }


    var body: some View {
        GroupBox(label:
            Label("End-User Agreement", systemImage: "building.columns")
        ) {
            ScrollView(.vertical, showsIndicators: true) {
                Text(agreementText)
                    .font(.footnote)
            }
            .frame(height: 100)
            Toggle(isOn: $userAgreed) {
                Text("I agree to the above terms")
            }
        }
    }


    struct PinkBorderGroupBoxStyle: GroupBoxStyle {
        func makeBody(configuration: Configuration) -> some View {
            GroupBox(configuration)
                .border(Color.pink)
        }
    }
    
    var body: some View {
        HStack(
            alignment: .top,
            spacing: 10
        ) {
            ForEach(
                1...5,
                id: \.self
            ) {
                Text("Item \($0)")
            }
        }
    }

        
        
    

    print(PaperSize(rawValue: "Legal"))
    // Prints "Optional("PaperSize.Legal")"

    print(PaperSize(rawValue: "Tabloid"))
    // Prints "nil"

    
    

    let selectedSize = PaperSize.Letter
    print(selectedSize.rawValue)
    // Prints "Letter"

    print(selectedSize == PaperSize(rawValue: selectedSize.rawValue)!)
    // Prints "true"
    
    Image("Landscape_4")
        .resizable()
        .aspectRatio(contentMode: .fit)
    Text("Water wheel")


    Image("dot_green")
        .renderingMode(.original)
    Image("dot_green")
        .renderingMode(.template)

    
```swift
HStack {
   Image(systemName: "person.crop.circle.badge.plus")
   Image(systemName: "person.crop.circle.badge.plus")
       .renderingMode(.original)
       .foregroundColor(.blue)
   Image(systemName: "person.crop.circle.badge.plus")
       .renderingMode(.template)
       .foregroundColor(.blue)
}
.font(.largeTitle)
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enum PaperSize: String {
    case A4, A5, Letter, Legal
}

print(PaperSize(rawValue: "Legal"))
// Prints "Optional("PaperSize.Legal")"

print(PaperSize(rawValue: "Tabloid"))
// Prints "nil"

    
    
    
HStack { Image(systemName: "swift").imageScale(.small); Text("Small") }
HStack { Image(systemName: "swift").imageScale(.medium); Text("Medium") }
HStack { Image(systemName: "swift").imageScale(.large); Text("Large") }


struct CircleImage_Previews: PreviewProvider {
    static var previews: some View {
        CircleImage()
            .previewInterfaceOrientation(.landscapeRight)
    }
}

Label("Lightning", systemImage: "bolt.fill")


Label("Lightning", systemImage: "bolt.fill")
    .labelStyle(.titleOnly)


Label("Lightning", systemImage: "bolt.fill")
    .labelStyle(.iconOnly)



Label("Lightning", systemImage: "bolt.fill")
    .labelStyle(.titleAndIcon)


struct RedBorderedLabelStyle: LabelStyle {
    func makeBody(configuration: Configuration) -> some View {
        Label(configuration)
            .border(Color.red)
    }
}



VStack {
    Label("Rain", systemImage: "cloud.rain")
    Label("Snow", systemImage: "snow")
    Label("Sun", systemImage: "sun.max")
}
.labelStyle(.iconOnly)


Label {
    Text(person.fullName)
        .font(.body)
        .foregroundColor(.primary)
    Text(person.title)
        .font(.subheadline)
        .foregroundColor(.secondary)
} icon: {
    Circle()
        .fill(person.profileColor)
        .frame(width: 44, height: 44, alignment: .center)
        .overlay(Text(person.initials))
}


struct RedBorderedLabelStyle: LabelStyle {
    func makeBody(configuration: Configuration) -> some View {
        Label(configuration)
            .border(Color.red)
    }
}


Label("Lightning", systemImage: "bolt.fill")
    .labelStyle(.titleAndIcon)



VStack {
    Label("Rain", systemImage: "cloud.rain")
    Label("Snow", systemImage: "snow")
    Label("Sun", systemImage: "sun.max")
}
.labelStyle(.titleAndIcon)


var rows: [GridItem] =
        Array(repeating: .init(.fixed(20)), count: 2)
ScrollView(.horizontal) {
    LazyHGrid(rows: rows, alignment: .top) {
        ForEach((0...79), id: \.self) {
            let codepoint = $0 + 0x1f600
            let codepointString = String(format: "%02X", codepoint)
            Text("\(codepointString)")
                .font(.footnote)
            let emoji = String(Character(UnicodeScalar(codepoint)!))
            Text("\(emoji)")
                .font(.largeTitle)
        }
    }
}

ScrollView(.horizontal) {
    LazyHStack(alignment: .top, spacing: 10) {
        ForEach(1...100, id: \.self) {
            Text("Column \($0)")
        }
    }
}

 var columns: [GridItem] =
         Array(repeating: .init(.flexible()), count: 2)
 ScrollView {
     LazyVGrid(columns: columns) {
         ForEach((0...79), id: \.self) {
             let codepoint = $0 + 0x1f600
             let codepointString = String(format: "%02X", codepoint)
             Text("\(codepointString)")
             let emoji = String(Character(UnicodeScalar(codepoint)!))
             Text("\(emoji)")
         }
     }.font(.largeTitle)
 }

ScrollView {
    LazyVStack(alignment: .leading) {
        ForEach(1...100, id: \.self) {
            Text("Row \($0)")
        }
    }
}

Link("View Our Terms of Service",
      destination: URL(string: "https://www.example.com/TOS.html")!)



func marketingLink(_ callToAction: String) -> Link {
    Link(callToAction,
        destination: URL(string: "https://www.example.com/")!)
}


var body: some View {
    List {
        Text("A List Item")
        Text("A Second List Item")
        Text("A Third List Item")
    }
}


struct Ocean: Identifiable {
    let name: String
    let id = UUID()
}
private var oceans = [
    Ocean(name: "Pacific"),
    Ocean(name: "Atlantic"),
    Ocean(name: "Indian"),
    Ocean(name: "Southern"),
    Ocean(name: "Arctic")
]

var body: some View {
    List(oceans) {
        Text($0.name)
    }
}



struct Ocean: Identifiable, Hashable {
    let name: String
    let id = UUID()
}
private var oceans = [
    Ocean(name: "Pacific"),
    Ocean(name: "Atlantic"),
    Ocean(name: "Indian"),
    Ocean(name: "Southern"),
    Ocean(name: "Arctic")
]
@State private var multiSelection = Set<UUID>()

var body: some View {
    NavigationView {
        List(oceans, selection: $multiSelection) {
            Text($0.name)
        }
        .navigationTitle("Oceans")
        .toolbar { EditButton() }
    }
    Text("\(multiSelection.count) selections")
}


struct Ocean: Identifiable, Hashable {
     let name: String
     let id = UUID()
     let stats: [String: String]
 }
 class OceanStore: ObservableObject {
     @Published var oceans = [Ocean]()
     func loadStats() async -> Void {}
 }
 @EnvironmentObject var store: OceanStore
 var body: some View {
     NavigationView {
         List(store.oceans) { ocean in
             HStack {
                 Text(ocean.name)
                 StatsSummary(stats: ocean.stats) // A custom view for showing statistics.
             }
         }
         .refreshable {
             await store.loadStats()
         }
         .navigationTitle("Oceans")
     }
 }


struct ContentView: View {
    struct Sea: Hashable, Identifiable {
        let name: String
        let id = UUID()
    }
    struct OceanRegion: Identifiable {
        let name: String
        let seas: [Sea]
        let id = UUID()
    }
    private let oceanRegions: [OceanRegion]  = [
        OceanRegion(name: "Pacific",
                    seas: [Sea(name: "Australasian Mediterranean"),
                           Sea(name: "Philippine"),
                           Sea(name: "Coral"),
                           Sea(name: "South China")]),
        OceanRegion(name: "Atlantic",
                    seas: [Sea(name: "American Mediterranean"),
                           Sea(name: "Sargasso"),
                           Sea(name: "Caribbean")]),
        OceanRegion(name: "Indian",
                    seas: [Sea(name: "Bay of Bengal")]),
        OceanRegion(name: "Southern",
                    seas: [Sea(name:"Weddell")]),
        OceanRegion(name: "Arctic",
                    seas: [Sea(name: "Greenland")])
    ]
    @State private var singleSelection : UUID?

    var body: some View {
        NavigationView {
            List(selection: $singleSelection){
                ForEach(oceanRegions) { region in
                    Section(header: Text("Major \(region.name) Ocean Seas")) {
                        ForEach(region.seas) { sea in
                            Text(sea.name)
                        }
                    }
                }
            }
            .navigationTitle("Oceans and Seas")
            .toolbar { EditButton() }
        }
    }
}


struct ContentView: View {
    struct FileItem: Hashable, Identifiable, CustomStringConvertible {
        var id: Self { self }
        var name: String
        var children: [FileItem]? = nil
        var description: String {
            switch children {
            case nil:
                return "
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