挑战

  • 将VStack表单中的每个替换为Section，其中文本视图是该部分的标题。你喜欢此布局还是该VStack布局？这是你的应用-你可以选择！
  • 用Picker显示相同数值范围的“杯数”步进器代替。
  • 更改用户界面，以使其始终使用漂亮的大字体显示建议的就寝时间。你应该可以完全删除“计算”按钮。

遇到的困难

ForEach数字循环需要从0开始
ForEach中第1个变量可以用 $0 代替
在此项目情境下，使用do catch组合时，return要放在do catch内。

代码

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import SwiftUI

struct ContentView: View {
    @State private var sleepAmount = 8.0
    @State private var wakeUp = Date()
    @State private var coffeePicker = 0
    @State private var coffeeAmount = 1
    
    //alert
    @State private var alertTitle = ""
    @State private var alertMessage = ""
    @State private var showingAlert = false
    
    var body: some View {
        NavigationView {
            Form {
                Section(header: Text("When do you want to wake up?")) {
                    DatePicker(selection: $wakeUp,displayedComponents: .hourAndMinute, label: {
                        Text("Please enter a date") })
                        .labelsHidden()
                }
                
                Section(header: Text("Desired amount of sleep")) {
                    Stepper(value: $sleepAmount, in: 4...12, step: 0.25) {
                        Text("\(sleepAmount, specifier: "%g") hours")
                    }
                }
                
                Section (header: Text("Daily coffee intake")) {
                    Picker(selection: $coffeePicker, label: Text("Daily coffee intake")) {
                        ForEach (0 ..< 20){
                            if $0 == 0 {
                                Text("1 cup")
                            }else{
                                Text("\(Int($0 + 1)) cups")
                            }
                        }
                        
                    }
                }
                
                Section(header: Text("Your ideal bedtime is")){
                    Text(sleeptime())
                        .font(.largeTitle)
                        .fontWeight(.bold)
                        .foregroundColor(Color.blue)
                        .frame(maxWidth: .infinity)
                    
                }
                
            }
            .navigationBarTitle("BetterRest")
                
            .alert(isPresented: $showingAlert){
                Alert(---
title: Text(alertTitle), message: Text(alertMessage), dismissButton: .default(Text("OK")))
            }
        }
    }
    
    func sleeptime() -> String {
        let model = SleepCalculator()
        let components = Calendar.current.dateComponents([.hour, .minute], from: wakeUp)
        let hour = (components.hour ?? 0) * 60 * 60
        let minute = (components.minute ?? 0) * 60
        
        do {
            coffeeAmount = coffeePicker + 1
            let prediction = try model.prediction(wake: Double(hour + minute), estimatedSleep: sleepAmount, coffee: Double(coffeeAmount)) //使用模型计算时间
            
            let sleepTime = wakeUp - prediction.actualSleep
            
            let formatter = DateFormatter()
            
            formatter.timeStyle = .short
            
            alertMessage = formatter.string(from: sleepTime)
            alertTitle = "Your ideal bedtime is ..."
            
            return formatter.string(from: sleepTime)
            
        } catch  {
            alertTitle = "Error"
            alertMessage = "Sorry there was a problem calculating your bedtime."
            showingAlert = true
            
            return "Error"
        }
        
        
       
        
    }
}

参考资料

查看下一天的SwiftUI学习笔记

关于100days英文课程