fun with oop

fun with oop

• dbsize

  This is very nice code, but I don't see where it addresses my question. I was hoping to pass a string parameter to a method and have the method return the correct object type. Anyone
  

• Knagis

  Public NotInheritable Class AnimalFactory
  Public Shared Sub Main()
  Dim ark As New List(Of Animal)
  Dim ns As String = GetType(Animal).Namespace
  ark.Add(AnimalFactory.Create(ns & ".Human"))
  ark.Add(AnimalFactory.Create(ns & ".Bird"))
  ark.Add(AnimalFactory.Create(ns & ".Cat"))
  ark.Add(AnimalFactory.Create(ns & ".Parrot"))
  ark.Add(AnimalFactory.Create(ns & ".Dog"))
  For Each beast As Animal In ark
  Console.WriteLine(beast.ToString())
  Next
  Console.ReadLine()
  End Sub
  
  Public Shared Function Create(ByVal animalname As String) As Animal
  Dim t As Type = Type.GetType(animalname, True, True)
  Dim args As String() = {animalname}
  Return Activator.CreateInstance(t, args)
  End Function
  End Class
  
  Public Class BodyParts
  Private constituentParts As New List(Of BodyParts)
  
  Public Sub New()
  End Sub
  
  Public Sub New(ByVal name As String)
  nameValue = name
  End Sub
  
  Private nameValue As String
  Public ReadOnly Property Name() As String
  Get
  Return nameValue
  End Get
  End Property
  
  Public Overrides Function ToString() As String
  If constituentParts.Count = 0 Then _
  Return nameValue & vbNewLine
  Dim s As String = String.Format("{0} has {1} parts{2}", _
  nameValue, constituentParts.Count, vbNewLine)
  For Each parts As BodyParts In constituentParts
  s += vbTab + parts.ToString()
  Next
  Return s
  End Function
  
  Public Sub Add(ByVal parts As BodyParts)
  constituentParts.Add(parts)
  End Sub
  End Class
  
  Public MustInherit Class Animal
  Inherits BodyParts
  
  Public Sub New()
  MyBase.New()
  End Sub
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  Build()
  End Sub
  
  Protected MustOverride Sub Build()
  
  Public Overridable Function Speak() As String
  Return ""
  End Function
  
  Public Overrides Function ToString() As String
  Return String.Format("{0} says: '{1}'{2}{3}", _
  Me.Name, Me.Speak, vbNewLine, MyBase.ToString)
  End Function
  End Class
  
  Public MustInherit Class FourLegged
  Inherits Animal
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Protected Overrides Sub Build()
  Dim frontlegs As New BodyParts("front legs")
  frontlegs.Add(New BodyParts("left front"))
  frontlegs.Add(New BodyParts("right front"))
  Dim hindlegs As New BodyParts("hind Legs")
  hindlegs.Add(New BodyParts("left hind"))
  hindlegs.Add(New BodyParts("right hind"))
  Me.Add(frontlegs)
  Me.Add(hindlegs)
  End Sub
  End Class
  
  Public MustInherit Class TwoLegged
  Inherits Animal
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Protected Overrides Sub Build()
  Dim legs As New BodyParts("legs")
  legs.Add(New BodyParts("left leg"))
  legs.Add(New BodyParts("right leg"))
  Me.Add(legs)
  End Sub
  End Class
  
  Public Class Cat
  Inherits FourLegged
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Public Overrides Function Speak() As String
  Return "Meow"
  End Function
  End Class
  
  Public Class Dog
  Inherits FourLegged
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Public Overrides Function Speak() As String
  Return "Woof"
  End Function
  End Class
  
  Public Class Bird
  Inherits TwoLegged
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Protected Overrides Sub Build()
  MyBase.Build()
  Dim wings As New BodyParts("wings")
  wings.Add(New BodyParts("left wing"))
  wings.Add(New BodyParts("right wing"))
  Me.Add(wings)
  End Sub
  
  Public Overrides Function Speak() As String
  Return "Tweet"
  End Function
  End Class
  
  Public Class Parrot
  Inherits Bird
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Public Overrides Function Speak() As String
  Return "Polly want a cracker"
  End Function
  End Class
  
  Public Class Human
  Inherits TwoLegged
  
  Public Sub New(ByVal name As String)
  MyBase.New(name)
  End Sub
  
  Protected Overrides Sub Build()
  MyBase.Build()
  Dim arms As New BodyParts("arms")
  arms.Add(New BodyParts("left arm"))
  arms.Add(New BodyParts("right arm"))
  Me.Add(arms)
  End Sub
  
  Public Overrides Function Speak() As String
  Return "Hello!"
  End Function
  End Class

  
  
  

• jacco2

  remember, ToString is a virtual method of object. override it for all your classes.

  
  
  

• Matthew Weyland

  hmmm. . . Actually it does. . . well not directly. You could change AnimalFactory to this:

  Public NotInheritable Class AnimalFactory
  Public Shared Sub Main()
  Dim ark As New List(Of Animal)
  Dim ns As String = GetType(Animal).Namespace
  ark.Add(AnimalFactory.Create(ns & ".Human"))
  ark.Add(AnimalFactory.Create(ns & ".Bird"))
  ark.Add(AnimalFactory.Create(ns & ".Cat"))
  ark.Add(AnimalFactory.Create(ns & ".Parrot"))
  ark.Add(AnimalFactory.Create(ns & ".Dog"))
  Console.WriteLine("Ark loaded by class name. . . ")
  Console.WriteLine(New String("-", 25))
  For Each beast As Animal In ark
  Console.WriteLine(beast.ToString())
  Next
  ark.Clear()
  ark.Add(AnimalFactory.CreateBySound("Hello"))
  ark.Add(AnimalFactory.CreateBySound("Tweet"))
  ark.Add(AnimalFactory.CreateBySound("Meow"))
  ark.Add(AnimalFactory.CreateBySound("Polly want a cracker"))
  ark.Add(AnimalFactory.CreateBySound("Woof"))
  Console.WriteLine(New String("-", 25))
  Console.WriteLine("Ark loaded by animal sound. . . ")
  Console.WriteLine(New String("-", 25))
  For Each beast As Animal In ark
  Console.WriteLine(beast.ToString())
  Next
  Console.ReadLine()
  End Sub
  
  Public Shared Function Create(ByVal animalname As String) As Animal
  Dim t As Type = Type.GetType(animalname, True, True)
  Dim args As String() = {animalname}
  Return Activator.CreateInstance(t, args)
  End Function
  
  Public Shared Function CreateBySound(ByVal sound As String) As Animal
  Dim ns As String = GetType(Animal).Namespace
  Select Case sound.ToUpper()
  Case "HELLO"
  Return AnimalFactory.Create(ns & ".Human")
  Case "TWEET"
  Return AnimalFactory.Create(ns & ".Bird")
  Case "MEOW"
  Return AnimalFactory.Create(ns & ".Cat")
  Case "POLLY WANT A CRACKER"
  Return AnimalFactory.Create(ns & ".PARROT")
  Case "WOOF"
  Return AnimalFactory.Create(ns & ".Dog")
  Case Else
  Throw New ArgumentException("Unknown Sound")
  End Select
  End Function
  End Class

  The point is. . .

  this is not OOP:

  Sub WriteToConsole(ByVal a As Animal)

  Dim writeString As String
  writeString = "Color: " & a.Color & ", " & "Legs: " & a.legs
  'can't write a.Wings to console from animal object
  'since this property is inherited from the bird class
  Console.WriteLine(writeString)

  End Sub

  Your class should know how to write itself via Animal.ToString() or Animal.WriteToConsole()

  I suggest you run the code I posted.

  
  
  
• fun with oop