挑战

最好的学习方法之一是尽可能频繁地编写自己的代码，因此，你应该尝试以下三种方式扩展此应用程序，以确保你完全了解正在发生的事情：

  • 添加一个@State属性来存储用户的分数，在答案正确与否时对其进行修改，然后将其显示在警报中。
  • 在标志正下方的标签中显示玩家的当前得分。
  • 如果有人选择了错误的标志，请在你的警报消息中告诉他们他们的错误-诸如“错误！那就是法国的国旗。”
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//
//  ContentView.swift
//  GuessTheFlag
//
//  Created by 张洪Hoo on 2020/1/20.
//  Copyright © 2020 张洪Hoo. All rights reserved.
//

import SwiftUI

struct ContentView: View {
    @State private var showingScore = false
    @State private var scoreTitle = ""
    @State private var score = 0
    
    @State private var countries = ["Estonia", "France", "Germany", "Ireland", "Italy", "Nigeria", "Poland", "Russia", "Spain", "UK", "US"].shuffled()
    @State private var correctAnswer = Int.random(in: 0...2)
    
    var body: some View {
        ZStack {
            LinearGradient(gradient: Gradient(colors: [.blue, .black]), startPoint: .top, endPoint: .bottom).edgesIgnoringSafeArea(.all)
            VStack(spacing: 30.0) {
                VStack {
                    Text("Tap the flag of")
                        .foregroundColor(Color.white)
                    
                    Text(countries[correctAnswer])
                        .font(.largeTitle)
                        .fontWeight(.black)
                        .foregroundColor(Color.white)
                    
                    Text("Score: \(score)")
                        .foregroundColor(Color.white)
                        .padding(.top)
                    
                }
                
                ForEach(0 ..< 3) { number in
                    Button(action: {
                        self.flagTapped(number)
                    }) {
                        Image(self.countries[number])
                            .renderingMode(.original)
                        .clipShape(Capsule())
                            .overlay(Capsule().stroke(Color.black, lineWidth: 1))
                            .shadow(color: .black, radius: 2)
                    }
                }
                Spacer()

            }
            
        }.alert(isPresented: $showingScore) {
            Alert(---
title: Text(scoreTitle), message: Text("Your score is \(score)"), dismissButton: .default(Text("Continue")))
        }
    }
    func flagTapped(_ number: Int) {
        if number == correctAnswer{
            scoreTitle = "Correct"
            self.score += 1
            
        }else {
            scoreTitle = "Wrong![]That's \(countries[number]) flag"
            self.score -= 1
        }
        
        showingScore = true
    }
    
    func askQuestion(){
        countries.shuffle()
        correctAnswer = Int.random(in: 0...2)
    }
}

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

参考资料

查看下一天的SwiftUI学习笔记

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