C# Switch 语句重构答案

【问题标题】：C# Switch Statement refactoringC# Switch 语句重构
【发布时间】：2009-11-25 15:26:04
【问题描述】：

以下代码的目的是确定特定日期是否符合“周末”条件，即周四下午 12:00 之后、至少 2 天和周一下午 12:00 之前

有没有更好的方法？ If-Else 变得丑陋，而 Strategy 模式的工作量太大了。

public bool ValidateWeekend(DateTime pickupDate, DateTime dropoffDate)
    {
        TimeSpan ts = dropoffDate.Subtract(pickupDate);

        if (ts.TotalDays >= 2 && ts.TotalDays <= 4)
        {
            switch (pickupDate.DayOfWeek)
            {
                case DayOfWeek.Thursday:
                    if (pickupDate.Hour >= 12)
                    {
                        switch (dropoffDate.DayOfWeek)
                        {
                            case DayOfWeek.Sunday:
                                return true;
                            case DayOfWeek.Monday:
                                if (dropoffDate.Hour <= 12)
                                {
                                    return true;
                                }
                                return false;
                        }
                    }
                    break;
                case DayOfWeek.Friday:
                    switch (dropoffDate.DayOfWeek)
                    {
                        case DayOfWeek.Sunday:
                            return true;
                        case DayOfWeek.Monday:
                            if (dropoffDate.Hour <= 12)
                            {
                                return true;
                            }
                            return false;
                    }
                    break;
                case DayOfWeek.Saturday:
                    switch (dropoffDate.DayOfWeek)
                    {
                        case DayOfWeek.Sunday:
                            return true;
                        case DayOfWeek.Monday:
                            if (dropoffDate.Hour <= 12)
                            {
                                return true;
                            }
                            return false;
                    }
                    return false;
            }
        }
        return false;
    }

【问题讨论】：

除了将重复的代码重构为下面列出的自己的方法之外，我还非常喜欢使用更实用的解决方案方法。将每一天的逻辑隔离到它自己的特定函数中，然后构建一个以天为键、以适当的方法为值的映射。正如我上面所说，通过将您的取货日期放入他们自己的方法中，然后使用 lamdas 执行您的丢弃逻辑，我认为代码变得更加清晰。

标签： c# refactoring switch-statement

【解决方案1】：

您绝对应该将 dropoffDate 重构出来 - 因为代码重复了 3 次！最简单的清理：我会引入一个函数来检查pickupDate，另一个来检查dropoffDate：

private bool IsPickupWeekend(DateTime pickupDate)
{
    switch (pickupDate.DayOfWeek)
            {
                case DayOfWeek.Thursday:
                    return pickupDate.Hour >= 12;
                case DayOfWeek.Friday:                    
                case DayOfWeek.Saturday:
                    return true;
            }
        }
        return false;
}

private bool IsWeekendDropOff(DateTime dropoffDate)
{
    switch (dropoffDate.DayOfWeek)
                    {
                        case DayOfWeek.Sunday:
                            return true;
                        case DayOfWeek.Monday:
                            if (dropoffDate.Hour <= 12)
                            {
                                return true;
                            }
                            return false;
                    }
                    return false;

}

现在你的主要功能是 2 班轮：

if (ts.TotalDays >= 2 && ts.TotalDays <= 4)
{
    return IsPickupWeekend(pickupDate) && IsWeekendDropOff(dropoffDate);
}

【讨论】：

很确定这将检查上午 12 点而不是下午 12 点
@Grzenio：IsWeekendDropOff 函数不应该将星期六作为 Drop Off 的日子吗？考虑到 PickUpDate 是星期四 1300 小时，那么 Drop Date 可以是星期六 1400 小时。
具体见msdn.microsoft.com/en-us/library/system.datetime.hour.aspx“小时分量，表示为0到23之间的值”
问题中提到的下午 12 点是中午 12 点，即 0-23 的时钟是 12 点，所以星期六不应该被视为 DropOff 的一天吗？ en.wikipedia.org/wiki/12-hour_clock
我刚刚从问题中复制了一些代码——作者只要求提供一个“不那么难看”的版本——所以我假设问题中的代码“正确”工作。

【解决方案2】：

我想你可以在这里提取一个方法：

private bool ValidateDropoff(DateTime dropoffDate)
{
    switch (dropoffDate.DayOfWeek)
    {
        case DayOfWeek.Sunday:
           return true;
        case DayOfWeek.Monday:
           return dropoffDate.Hour <= 12;
        default:
           return false;
    }
}

【讨论】：

你需要一个'return false;'在末尾;否则，并非每条路径都会返回一个值。或者，只需移动'return false;'你在开关之外。
@Gorpik，默认情况下会处理这个问题。实际上，每条路径都会返回一个值。
星期六不应该是这个代码中的一个案例吗？如果 PickUpDate：星期四 1300 Hr 和 Drop Date：星期六 1400 Hr，请告诉我此代码是否有效？

【解决方案3】：

if (ts.TotalDays >= 2 && ts.TotalDays <= 4)
{
    var hour_limit = new Func<Boolean>(() => {
        switch (dropoffDate.DayOfWeek)
        {
            case DayOfWeek.Sunday:
                return true;
            case DayOfWeek.Monday:
                return dropoffDate.Hour <= 12;
            default:
                return false;
        }

    });

    switch (pickupDate.DayOfWeek)
    {
        case DayOfWeek.Thursday:
            if (pickupDate.Hour >= 12)  return hour_limit();
            break;
        case DayOfWeek.Friday:
        case DayOfWeek.Saturday:
            return hour_limit();
        default: 
            break;
    }
}

return false;

【讨论】：

【解决方案4】：

不是很清楚，但是你去吧：

public bool ValidateWeekend(DateTime pickupDate, DateTime dropoffDate){
    TimeSpan ts = dropoffDate.Subtract(pickupDate);

    if (ts.TotalDays >= 2 && ts.TotalDays <= 4){
        switch (pickupDate.DayOfWeek){
            case DayOfWeek.Thursday:
                if (pickupDate.Hour >= 12){
                    switch (dropoffDate.DayOfWeek){
                        case DayOfWeek.Sunday:
                            return true;
                        case DayOfWeek.Monday:
                            return dropoffDate.Hour <= 12;
                    }
                }
                break;
            case DayOfWeek.Friday:
                switch (dropoffDate.DayOfWeek){
                    case DayOfWeek.Sunday:
                        return true;
                    case DayOfWeek.Monday:
                        return dropoffDate.Hour <= 12;
                }
                break;
            case DayOfWeek.Saturday:
                switch (dropoffDate.DayOfWeek){
                    case DayOfWeek.Sunday:
                        return true;
                    case DayOfWeek.Monday:
                        return dropoffDate.Hour <= 12;
                }
                return false;
        }
    }
    return false;
}

【讨论】：

【解决方案5】：

我的第一次破解：

if (ts.TotalDays >= 2 && ts.TotalDays <= 4)
        {
            switch (pickupDate.DayOfWeek)
            {
                case DayOfWeek.Thursday:
                case DayOfWeek.Friday:
                case DayOfWeek.Saturday:
                    if (pickupDate.DayOfWeek == DayOfWeek.Thursday && pickupDate.Hour <= 12)
                        return false;

                    switch (dropoffDate.DayOfWeek)
                    {
                        case DayOfWeek.Sunday:
                            return true;
                        case DayOfWeek.Monday:
                            return dropoffDate.Hour <= 12;
                    }
                    return false;

                default:
                    return false;
            }
        }
        return false;

【讨论】：

【解决方案6】：

在switch中尝试

retrun (dropoffDate.DayOfWeek == DayOfWeek.Sunday && dropoffDate.Hour <= 12 || dropoffDate.DayOfWeek == DayOfWeek.Sunday)

【讨论】：

【解决方案7】：

我会这样做

public bool ValidateWeekend(DateTime pickupDate, DateTime dropoffDate)
{
    TimeSpan ts = dropoffDate.Subtract(pickupDate);

    if (ts.TotalDays >= 2 && ts.TotalDays <= 4)
    {
        switch (pickupDate.DayOfWeek)
        {
            case DayOfWeek.Thursday:
                if (pickupDate.Hour >= 12)
                {
                    reurn DayOfWeek(dropOffDate.DayOfWeek);
                }
                break;
            case DayOfWeek.Friday, DayOfWeek.Saturday:
                {
                    return DayOfWeek(dropOffDate.DayOfWeek);
                }
        }
    }
    return false;
}

public bool DayOfWeek(DateTime dropOffDate)
    {
switch (dropoffDate.DayOfWeek)
    {
        case DayOfWeek.Sunday:
            {
                return true;
            }
        case DayOfWeek.Monday:
            {
                if (dropoffDate.Hour <= 12)
                    {
                        return true;
                    }
                return false;
            }
       return false;
   }
 }

【讨论】：

【解决方案8】：

这是我的尝试：

  /// <summary>
    /// Gets the weekend days.
    /// </summary>
    /// <returns></returns>
    public List<DayOfWeek> GetWeekendDays()
    {
        List<DayOfWeek> days = new List<DayOfWeek>()
                                   {
                                       DayOfWeek.Thursday,
                                       DayOfWeek.Friday,
                                       DayOfWeek.Sunday
                                   };
        return days;
    }

    /// <summary>
    /// Validates the weekend.
    /// </summary>
    /// <param name="pickupDate">The pickup date.</param>
    /// <param name="dropoffDate">The dropoff date.</param>
    /// <returns></returns>
    public bool ValidateWeekend(DateTime pickupDate, DateTime dropoffDate)
    {
        bool isValid = false;
        TimeSpan ts = dropoffDate.Subtract(pickupDate);

        if (ts.TotalDays >= 2 && ts.TotalDays <= 4)
        {
            List<DayOfWeek> days = GetWeekendDays();

            foreach (DayOfWeek day in days)
            {
                if(pickupDate.DayOfWeek == day)
                {
                   isValid = ValidateDropOff(dropoffDate);
                    break;
                }
            }
        }

        return isValid;
    }

    /// <summary>
    /// Validates the drop off.
    /// </summary>
    /// <param name="dropoffDate">The dropoff date.</param>
    /// <returns></returns>
    private static bool ValidateDropOff(DateTime dropoffDate)
    {
        bool isValidDropOff = (dropoffDate.DayOfWeek == DayOfWeek.Sunday);

        if(dropoffDate.DayOfWeek == DayOfWeek.Monday)
        {
            if (dropoffDate.Hour <= 12)
            {
                isValidDropOff = true;
            }
        }

        return isValidDropOff;
    }

【讨论】：

【解决方案9】：

    private readonly TimeSpan Midday = new TimeSpan(12, 0, 0);

    public bool ValidateWeekend(DateTime pickupDate, DateTime dropoffDate)
    {
        TimeSpan lengthOfTrip = dropoffDate.Subtract(pickupDate);

        if (lengthOfTrip.TotalDays < 2 || lengthOfTrip.TotalDays > 4)
            return false;

        return IsPickupDateConsideredWeekend(pickupDate) && IsDropoffDateConsideredWeekend(dropoffDate);
    }

    private bool IsPickupDateConsideredWeekend(DateTime pickupdate)
    {
        if (pickupdate.DayOfWeek == DayOfWeek.Thursday && pickupdate.TimeOfDay > Midday)
            return true;
        return false;
    }

    private bool IsDropoffDateConsideredWeekend(DateTime dropoffDate)
    {
        if (dropoffDate.DayOfWeek == DayOfWeek.Monday && dropoffDate.TimeOfDay <= Midday)
            return true;
        return false;
    }

【讨论】：