处理错误

本课属于 Coddy Swift 学习旅程的“基础知识”单元。第 83 课，共 86 课。

挑战

简单

在上一课中，你实现了“清除所有支出”功能。现在，为支出跟踪器中的无效输入添加错误处理。

修改代码，妥善处理无效输入：

当用户输入无效的菜单选项（除 "1"、"2"、"3"、"4" 或 "5" 以外的任何内容）时，输出 Invalid option. Please try again.
添加支出时（选项 "1"），如果输入无法转换为有效的 Double，输出 Invalid amount. Expense not added.，然后返回菜单，不要向数组中添加任何内容
其他所有功能都应继续像以前一样正常运行

预期行为：

输入无效的菜单选项时，显示错误消息并再次显示菜单
输入无效的支出金额时，显示错误消息并返回菜单
有效输入仍能像前几课中实现的那样正常运行

交互示例：

1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
7
Invalid option. Please try again.
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
1
Enter expense amount:
abc
Invalid amount. Expense not added.
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
1
Enter expense amount:
25.0
Expense added!
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
2
Your expenses:
- $25.0
1. Add expense
2. View all expenses
3. Show total and average
4. Clear all expenses
5. Exit
5
Goodbye!

亲手试试

// Daily Expense Tracker - Menu Display

var expenses: [Double] = []

while true {
    // TODO: Write your code below to print the menu options
    // Each option should be on its own line with the format: "number. option text"
    print("1. Add expense")
    print("2. View all expenses")
    print("3. Show total and average")
    print("4. Clear all expenses")
    print("5. Exit")
    
    let choice = readLine()
    
    if choice == "1" {
        print("Enter expense amount:")
        if let input = readLine(), let amount = Double(input) {
            expenses.append(amount)
            print("Expense added!")
        }
    } else if choice == "2" {
        if expenses.isEmpty {
            print("No expenses recorded.")
        } else {
            print("Your expenses:")
            for expense in expenses {
                print("- $\(expense)")
            }
        }
    } else if choice == "3" {
        if expenses.isEmpty {
            print("No expenses to calculate.")
        } else {
            let total = expenses.reduce(0, +)
            let average = total / Double(expenses.count)
            print("Total: $\(total)")
            print("Average: $\(average)")
        }
    } else if choice == "4" {
        expenses.removeAll()
        print("All expenses cleared!")
    } else if choice == "5" {
        print("Goodbye!")
        break
    } else {
        print("Coming soon...")
    }
}

基础知识中的所有课

自己练习： Swift 在线编辑器