如果输入无效数据,如何重复代码

Question

我需要制作计算停车费的代码给出错误并要求用户在提供错误号码时重新输入数据.例如,如果用户输入的金额小于1或大于24,则会出现错误代码并要求用户重新输入有效金额.输入有效金额后,我希望输出parkFee.我没有更新我的伪代码,所以对此表示歉意.

    /* PSEUDOCODE */
    /* HOURLY_RATE=2.5
     * INPUT parkTime
     * parkFee = HOURLY_RATE * hours
     * OUTPUT parkFee */


        decimal parkTime;  // input - time in hour eg 1.5 for 1 and a half hours 
        const decimal HOURLY_RATE = 2.50m; // HOURLY_RATE * INPUT parkTime = parkFee
        const decimal MAX_FEE = 20.00m; // MAX_FEE is set as a payment cap and ignores any extra charges incurred over 8 hours
        decimal parkFee;
        Console.WriteLine("ParkingFee1 program developed by: Ryley Copeman");
        Console.WriteLine("Please enter your total time parked in hours: Eg 1.5 or 3.0");
        parkTime = decimal.Parse(Console.ReadLine());

        if (parkTime > 8)
        {
            Console.Write("Total fee is $" + MAX_FEE);
        }
        else
        {
            parkFee = Math.Ceiling(parkTime) * HOURLY_RATE;
            Console.Write("Parking Fee = $" + parkFee);
        }
        while(parkTime < 0 || parkTime > 24)    // validate... 
        //while (parkTime <= 0) )
        {
        Console.WriteLine("Error – Park Time out of range");
        Console.WriteLine("Enter - Park Time between 0 and 24 (HOURS):");
        parkTime = int.Parse(Console.ReadLine());

    }

    }
}

}

Answer 1

我想你只需要这个:

do
{
    Console.WriteLine("Please enter your total time parked in hours: Eg 1.5 or 3.0");
    parkTime = decimal.Parse(Console.ReadLine());

    if (parkTime < 1 || parkTime > 24)
    {
        Console.WriteLine("Error – Park Time out of range");
    }
}
while (parkTime < 1 || parkTime > 24);

if (parkTime > 8)
{
    Console.Write("Total fee is $" + MAX_FEE);
}
else
{
     parkFee = Math.Ceiling(parkTime) * HOURLY_RATE;
     Console.Write("Parking Fee = $" + parkFee);
 }

请注意,您可能需要调整代码以始终计算费用,然后应用最大值:

parkFee = Math.Min(MAX_FEE, Math.Ceiling(parkTime) * HOURLY_RATE);
Console.Write("Parking Fee = $" + parkFee);

这里Math.Min将选择两个值中最小的一个.

最后,请注意,decimal.Parse如果您输入了不期望的内容(例如"1.2Hello"或""),则会出错,因此最好使用TryParse:

bool isValidTime = false;
do
{
    Console.WriteLine("Please enter your total time parked in hours: Eg 1.5 or 3.0");
    bool parsedOK = decimal.TryParse(Console.ReadLine(), out parkTime);
    isValidTime = parsedOK && parkTime >= 1 && parkTime <= 24;
    if (!isValidTime)
    {
        Console.WriteLine("Error – Park Time out of range");
    }
}
while (!isValidTime);

parkFee = Math.Min(MAX_FEE, Math.Ceiling(parkTime) * HOURLY_RATE);
Console.Write("Parking Fee = $" + parkFee);

这里循环将继续,直到输入有效值.请注意,在循环结构中,您还可以使用break;(保留循环)和continue;(移动到循环的下一次迭代)来控制流.