Abstract Factory

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Oct 11, 2013

CPOL

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Abstract FactoryThe Gang of Four defintion for this design pattern is: "Provide an interface for creating families of related or dependant objects

Abstract Factory

The Gang of Four defintion for this design pattern is: "Provide an interface for creating families of related or dependant objects without specifying their concrete classes.".

A VB example of the Abstract Factory Design Pattern

' This code could be run at the page behind level
Dim aCarFactory As CarFactory

' Ideally we would use the Factory Design pattern
' but I omitted this for simplicity
If aVariable = "Ford" Then
     aCarFactory = New FordCarFactory
Else
     aCarFactory = New VauxhallCarFactory
End If
' Build 2 family cars
Dim aFamilyCar1 As ICar = aCarFactory.CreateFamilyCar
Dim aFamilyCar2 As ICar = aCarFactory.CreateFamilyCar ' Build a City Car
Dim aCityCar As ICar = aCarFactory.CreateCityCar

' The base class Car Factory
Public MustInherit Class CarFactory
    Public MustOverride Function CreateFamilyCar() As ICar
    Public MustOverride Function CreateCityCar() As ICar
End Class

' The concrete Ford car factory
Public Class FordCarFactory
    Inherits CarFactory     Public Overrides Function CreateCityCar() As ICar
         Return New FordCityCar
    End Function
    Public Overrides Function CreateFamilyCar() As ICar
         Return New FordFamilyCar
    End Function
End Class

' The concrete Vauxhall car factory
Public Class VauxhallCarFactory
    Inherits CarFactory     Public Overrides Function CreateCityCar() As ICar
        Return New VauxhallCityCar
    End Function
    Public Overrides Function CreateFamilyCar() As ICar
        Return New VauxhallFamilyCar
    End Function
End Class

' The Car Interface, all cars must implement these methods
Public Interface ICar
 
    Sub Drive()     

    Function Desc() As String

End Interface

' The concrete Ford Family Car
Public Class FordFamilyCar
    Implements ICar     Public Sub Drive() Implements ICar.Drive
       ' Drive car
    End Sub
    Public Function Desc() As String Implements ICar.Desc
       Return "Ford Family Car seats 8"
    End Function
End Class

' The concrete Ford City Car
Public Class FordCityCar
    Implements ICar     Public Sub Drive() Implements ICar.Drive
       ' Drive car
    End Sub
    Public Function Desc() As String Implements ICar.Desc
       Return "Ford Ciy Car seats 2"
    End Function
End Class

' The concrete Vauxhall City Car
Public Class VauxhallCityCar
    Implements ICar     Public Sub Drive() Implements ICar.Drive
       ' Drive car
    End Sub
    Public Function Desc() As String Implements ICar.Desc
        Return "Vauxhall Ciy Car seats 4"
    End Function
End Class

' The concrete Vauxhall Family Car
Public Class VauxhallFamilyCar
    Implements ICar     Public Sub Drive() Implements ICar.Drive
        ' Drive car
    End Sub
    Public Function Desc() As String Implements ICar.Desc
        Return "Vauxhall Family Car seats 6"
    End Function
End Class

External links

Abstract factory