将一个值设置为不断变化的默认值

Question

I am creating a game where I have a value of highscore which I want to save each time it is updated even if I exit the app. I have already the value of highscore which updates eveyrtime the score > highscore but if I exit the app, it the highscore resets to 0 and I want it to maintain.

import SwiftUI

struct Europe: View {
    @State private var countries = ["Albania", "etc."].shuffled()
    
    @State private var corrrectAnswer = Int.random(in: 0...5)
    @State private var showingScore = false
    @State private var scoreTitle = ""
    @State private var userScore = 0
    @State private var highScore = 0
    

    var body: some View {
        ZStack{
            LinearGradient(gradient: Gradient(colors: [.white,.blue]), startPoint: .top, endPoint: .bottom).edgesIgnoringSafeArea(.all)
            VStack(spacing:30){
                VStack{
                    Text("Tap the flag of")
                        .foregroundColor(.black)
                        .fontWeight(.black)
                    Text(countries[corrrectAnswer])
                        .foregroundColor(.black)
                        .font(.largeTitle)
                        .fontWeight(.black)
                }
                
                VStack(spacing:50){
                    
                    HStack(spacing:40) {
                        VStack(spacing:40) {
                            ForEach(0..<3){ number in
                                Button(action: {
                                    self.flagTapped(number)
                                    self.highScoreSet(number)
                                }){
                                    Image(self.countries[number])
                                        .resizable()
                                            .frame(width: 130, height: 100)
                                        .clipShape(Capsule())
                                        .overlay(Capsule().stroke(Color.black,lineWidth: 1))
                                        .shadow(color: .black, radius: 2)
                                }
                                
                                
                            }
                        }
                        VStack(spacing:40) {
                            ForEach(4..<7){ number in
                                Button(action: {
                                    self.flagTapped(number)
                                    self.highScoreSet(number)
                                }){
                                    Image(self.countries[number])
                                        .resizable()
                                            .frame(width: 130, height: 100)
                                        .clipShape(Capsule())
                                        .overlay(Capsule().stroke(Color.black,lineWidth: 1))
                                        .shadow(color: .black, radius: 2)
                                }
                                
                                
                            }
                        }
                    }
                    
                    VStack{
                        Text("Score:  \(userScore)")
                            .foregroundColor(.white)
                            .fontWeight(.black)
                            .font(.subheadline)
                        
                        Text("High Score: \(highScore)")

                            .foregroundColor(.white)
                            .fontWeight(.black)
                            .font(.subheadline)
                        

                    }

                    Spacer()
                }
            }
        }
        .alert(isPresented: $showingScore){
            Alert(title: Text(scoreTitle), message: Text("Your score is \(userScore)"), dismissButton: .default(Text("Continue")){
                self.askQuestion()})
        }
    }

    func highScoreSet(_ number: Int){
        if highScore < userScore {
            highScore = userScore
        }
    }

    func flagTapped(_ number: Int){
        if number == corrrectAnswer{
            scoreTitle = "Right"
            userScore += 1
        }
        else {
            scoreTitle = "Wrong!\n Thats the flag of \(countries[corrrectAnswer])"
            userScore = 0
        }
        showingScore = true
    }

    func askQuestion(){
        countries.shuffle()
        corrrectAnswer = Int.random(in: 0...5)
    }
    
}

struct Europe_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Answer 1

You can use the @AppStorage property wrapper. Good article here on how to use it.

Change:

@State private var highScore = 0

To:

@AppStorage("high_score") private var highScore = 0