在软件设计工厂模式中使用抽象泛型类

Question

嘿家伙我有一点设计问题.我创建了一个率计算器,如下所示:

Public Interface ICalculator
 Property PaymentTerm As Double
 Function Calculate() As CommissionValues
 ReadOnly Property CalculationRule As CalculationRuleEnum
End Interface

Public Interface IFlexibleRateCalculator
 Inherits ICalculator
  Property TransferRate As Decimal
End Interface

Public Interface IFixedRateCalculator
 Inherits ICalculator
  Property ContractRate As Decimal
End Interface

Public Interface IRateSettingBase
  Property RateType As RateTypeEnum
  ReadOnly Property Calculator As ICalculator
End Interface

Public MustInherit Class RateSetting
 Implements IRateSettingBase
  Public MustOverride ReadOnly Property Calculator() As ICalculator Implements IRateSettingBase.Calculator

我可以这样做:

dim ratevalues as RateValues = RateSetting().Calculator.Calculate()

很简单.问题是每种类型的计算器都有自己的属性集,需要设置它们才能使Calculate()方法正常工作.所以我最终必须实现如下

FlexibleRateCalculator
Implements IFlexibleRateCalculator
    Private mRequestedRate As Decimal
    Public Function Calculate() As RateValues Implements ICalculator.Calculate

FixedRateCalculator
 Implements IFixedRateCalculator
    Private mTransferRate As Decimal
    Public Function Calculate() As RateValues Implements ICalculator.Calculate

使用泛型和抽象类创建工厂模式以动态生成特定类型的计算器的最佳方法是什么？

我需要一个非常通用的解决方案,因为许多计算速率将被添加和修改所有计算逻辑所需的参数.我希望能够快速完成此操作并可能通过db控制这些速率计算.欢迎在C#或VB.Net的FYI答案:)提前感谢!

Answer 1

仅保留ICalculator接口，并将更具体的接口转换为类。我想不出为什么要创建一个类只是为了存储变量的好理由，所以我将RateSetting完全摆脱它。

Public Interface ICalculator
    Property Rate As Double
    Property PaymentTerm As Double
    Function Calculate() As CommissionValues
    ReadOnly Property CalculationRule As CalculationRuleEnum
End Interface

Public Class FlexibleRateCalculator : Implements ICalculator

    Public Sub New(rate As Double)
        Me.Rate = rate
    End Sub

    '
    ' ICalculator implementation goes here
    '

End Class

Public Class FixedRateCalculator : Implements ICalculator

    Public Sub New(rate As Double)
        Me.Rate = rate
    End Sub

    '
    ' ICalculator implementation goes here
    '

End Class

Public Enum RateType
    Flexible = 1
    Fixed = 2
End Enum

Public Class CalculatorFactory

    Public Shared Function GetCalculator(rate As Double, type As RateType) As ICalculator
        Select Case type
            Case RateType.Flexible
                Return New FlexibleRateCalculator(rate)
            Case RateType.Fixed
                Return New FixedRateCalculator(rate)
            Case Else
                Throw New ArgumentException
        End Select
    End Function

End Class

您可以通过将速率和速率类型传递给该GetCalculator方法来创建对象实例。我不知道你的意思CalculationRule，但如果它对最终用户很重要，那么你应该将其添加为附加参数。

只要您不忘记更新工厂方法中的 select 语句，您就可以轻松添加更多实现 ICalculator 的计算器类型。

编辑：当然，您还可以在返回对象实例之前设置其他属性。然而，这种模式的要点是确保最终用户不需要知道如何Calculate()实现。如果您想为每个计算器创建更具体的工厂方法，那么它就达不到目的了。