1. AppStorage 数据简单存储的实现

/// 应用程序数据简单存储
struct AppStorageBootcamp: View {
    
    //@State var currentUserName: String?
    @AppStorage("name") var currentUserName: String?
    
    var body: some View {
        VStack(spacing: 20) {
            Text(currentUserName ?? "Add Name Here")
            
            if let name = currentUserName {
                Text(name)
            }
            
            Button("Save".uppercased()) {
                let name:String  = "Emily"
                currentUserName = name
                // 用户默认值
                //UserDefaults.standard.set(name, forKey: "name")
            }
        }
//        .onAppear {
//            currentUserName = UserDefaults.standard.string(forKey: "name")
//        }
    }
}

2. OnboardingView 引导页的示例

  2.1 OnboardingView 引导页的实现

// 引导页 View
struct OnboardingView: View {
    
    // 引导页状态:
    /*
     0  — 欢迎进入
     1  — 添加名字
     2  — 添加年龄
     3  — 添加性别
     */
    @State var onboardingState: Int = 0
    
    let transition: AnyTransition = .asymmetric(
        insertion: .move(edge: .trailing),
        removal: .move(edge: .leading))
    
    /// 输入名字文本框
    @State var name: String = ""
    /// 年龄值
    @State var age: Double = 50
    /// 性别
    @State var gender: String = "Male"
    
    // 警告框
    @State var alertTitle: String = ""
    @State var showAlert: Bool = false
    
    // app 存储
    @AppStorage("name") var currentUserName: String?
    @AppStorage("age") var currentUserAge: Int?
    @AppStorage("gender") var currentUserGender: String?
    @AppStorage("signed_in") var currentUserSignedIn: Bool = false
    
    var body: some View {
        
        ZStack{
            // content
            ZStack{
                switch onboardingState{
                case 0:
                    welcomeSection
                        .transition(transition)
                case 1:
                    addNameSection
                        .transition(transition)
                case 2:
                    addAgeSection
                        .transition(transition)
                case 3:
                    addGenderSection
                        .transition(transition)
                default:
                    RoundedRectangle(cornerRadius: 25)
                        .foregroundColor(.green)
                }
            }
            
            // buttons
            VStack{
                Spacer()
                bottomButton
            }
            .padding(30)
        }
        .alert(isPresented: $showAlert) {
            return Alert(title: Text(alertTitle))
        }
    }
}

struct OnboardingView_Previews: PreviewProvider {
    static var previews: some View {
        OnboardingView()
            .background(Color.purple)
    }
}

// MARK: COMPONENTS 扩展类

extension OnboardingView{
    
    /// 登录按钮
    private var bottomButton: some View{
        Text(onboardingState == 0 ? "SIGN UP" :
                onboardingState == 3 ? "FINISH" :
                "NEXT")
        .font(.headline)
        .foregroundColor(.purple)
        .frame(height: 55)
        .frame(maxWidth: .infinity)
        .background(Color.white)
        .cornerRadius(10)
        .animation(nil) //去掉按钮动画
        .onTapGesture {
            handleNextButtonPressed()
        }
    }
    
    /// 欢迎页
    private var welcomeSection: some View{
        VStack(spacing: 40) {
            Spacer()
            Image(systemName: "heart.text.square.fill")
                .resizable()
                .scaledToFit()
                .frame(width: 200, height: 200)
                .foregroundColor(.white)
            
            Text("Find your match.")
                .font(.largeTitle)
                .fontWeight(.semibold)
                .foregroundColor(.white)
                .overlay(
                    Capsule(style: .continuous)
                        .frame(height: 3)
                        .offset(y: 5)
                        .foregroundColor(.white)
                    , alignment: .bottom
                )
            Text("This is the #1 app for finding your match online! In this tutotial, we are practicing using AppStorage and Swift UI techniques.")
                .foregroundColor(.white)
                .fontWeight(.medium)
            Spacer()
            Spacer()
        }
        .multilineTextAlignment(.center)
        .padding(30)
    }
    
    /// 添加名字
    private var addNameSection: some View{
        VStack(spacing: 20) {
            Spacer()
            Text("What's your name?")
                .font(.largeTitle)
                .fontWeight(.semibold)
                .foregroundColor(.white)
            TextField("Your name here...", text: $name)
                .font(.headline)
                .frame(height: 55)
                .padding(.horizontal)
                .background(Color.white)
                .cornerRadius(10)
            
            Spacer()
            Spacer()
        }
        .padding(30)
    }
    
    /// 添加年龄
    private var addAgeSection: some View{
        VStack(spacing: 20) {
            Spacer()
            Text("What's your age?")
                .font(.largeTitle)
                .fontWeight(.semibold)
                .foregroundColor(.white)
            
            Text("\(String(format: "%.0f", age))")
                .font(.largeTitle)
                .fontWeight(.semibold)
                .foregroundColor(.white)
            Slider(value: $age, in: 18...100, step: 1)
                .accentColor(.white)
            Spacer()
            Spacer()
        }
        .padding(30)
    }
    
    /// 添加性别
    private var addGenderSection: some View{
        VStack(spacing: 20) {
            Spacer()
            Text("What's your gender?")
                .font(.largeTitle)
                .fontWeight(.semibold)
                .foregroundColor(.white)
            
            Picker(selection: $gender) {
                Text("Male").tag("Male")
                Text("Female").tag("Female")
                Text("Non-Binary").tag("Non-Binary")
            } label: {
                Text(gender.count > 1 ? gender : "Select a gender")
                    .font(.headline)
                    .foregroundColor(.purple)
                    .frame(height: 55)
                    .frame(maxWidth: .infinity)
                    .cornerRadius(10)
            }
            .pickerStyle(.menu)
            .accentColor(.white)
            Spacer()
            Spacer()
        }
        .padding(30)
    }
}

// MARK: FUNCTIONS

extension OnboardingView{
    func handleNextButtonPressed(){
        // CHECK INPUTS
        switch onboardingState{
        case 1:
            guard name.count >= 3 else{
                showAlert(title: "你的名字必须要有3个字符的长度！😩")
                return
            }
        case 3:
            guard gender.count > 1 else{
                showAlert(title: "请在下一步之前选择一个性别！😳")
                return
            }
        default:
            break
        }
        // GO TO NEXT SECTION
        if onboardingState == 3{
            // sign in
            signIn()
        }else{
            // spring 弹簧
            withAnimation(.spring()) {
                onboardingState += 1
            }
        }
    }
    
    // 登录
    func signIn(){
        currentUserName = name
        currentUserAge = Int(age)
        currentUserGender = gender
        
        // 添加动画
        withAnimation(.spring()) {
            currentUserSignedIn = true
        }
    }
    
    /// 输出警告框
    func showAlert(title: String){
        alertTitle = title
        showAlert.toggle()
    }
}

  2.2 ProfileView 信息页的实现

/// 信息页 View
struct ProfileView: View {
    // app 存储
    @AppStorage("name") var currentUserName: String?
    @AppStorage("age") var currentUserAge: Int?
    @AppStorage("gender") var currentUserGender: String?
    @AppStorage("signed_in") var currentUserSignedIn: Bool = false
    
    var body: some View {
        VStack(spacing: 10){
            Image(systemName: "person.circle.fill")
                .resizable()
                .scaledToFit()
                .frame(width: 150, height: 150)
            Text(currentUserName ?? "Your name here")
            Text("This user is \(currentUserAge ?? 0) years old")
            Text("Their gender is \(currentUserGender ?? "unknown")")
            
            Text("SIGN OUT")
                .foregroundColor(.white)
                .font(.headline)
                .frame(height: 55)
                .frame(maxWidth: .infinity)
                .background(Color.black)
                .cornerRadius(10)
                .onTapGesture {
                    signOut()
                }
        }
        .font(.title)
        .foregroundColor(.purple)
        .padding()
        .padding(.vertical)
        .background(Color.white)
        .cornerRadius(10)
        .shadow(radius: 10)
    }
    
    /// 退出
    func signOut(){
        currentUserName = nil
        currentUserAge = nil
        currentUserGender = nil
        withAnimation(.spring()){
            currentUserSignedIn = false
        }
    }
}

  2.3 IntroView 简介视图

/// 简介视图
struct IntroView: View {
    @AppStorage("signed_in") var currentUserSignedIn: Bool = false
    
    var body: some View {
        ZStack{
            // background
            RadialGradient(
                gradient: Gradient(colors: [Color(#colorLiteral(red: 0.8446564078, green: 0.5145705342, blue: 1, alpha: 1)),Color(#colorLiteral(red: 0.3647058904, green: 0.06666667014, blue: 0.9686274529, alpha: 1))]),
                center: .topLeading,
                startRadius: 5,  // 开始半径
                endRadius: UIScreen.main.bounds.height) // 结束半径
            .ignoresSafeArea()
            
            if currentUserSignedIn {
                // 显示详情页
                ProfileView()
                // 添加动画
                    .transition(.asymmetric(insertion: .move(edge: .bottom), removal: .move(edge: .top)))
            }else{
                // 登记页
                OnboardingView()
                // 添加动画
                    .transition(.asymmetric(insertion: .move(edge: .top), removal: .move(edge: .bottom)))
            }
            // 用户是否已经登录
            // 显示个人资料视图
            // 否则
            // 填写引导视图
        }
    }
}

  2.4 效果图: