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
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