Old McDonnald Had A Farm E - I - E - I _ O!

[Fred Harris]

Was > Old McDonnald Had A Farm E - I - E - I _ O!

Probably the single most used example in textbooks that teach OOP is something having to do with animals. For example, the term animal is a rather general term. However, there are some characteristics that all animal have such as ability to move and eat. If you become more specific and consider for example horses or sheep, their behaviors are more specific in terms of how they move and what they eat. Below is a class 'Animal' which is further specialized with additional inheriting classes 'horse' and 'sheep'. These latter classes inherit and override the behaviors of 'animal'.

#Compile Exe     '''Console Compiler 5.0
#Dim All

Interface ICare : Inherit IUnknown     'According to Mr. Zale, an interface is a "set of methods
  Method Groom() As String             'and properties which are implemented on an object.  You
  Method Deworm() As String            'might think of it as a list of DECLARE statements where
End Interface                          'the sequence of the Declares must be preserved.  Remember,
                                       'the interface is just the definition, not the actual code.
                                       '...An interesting note is that one particular interface
Class Animal                           'definition may become a part of several different classes
  Instance m_strName As String         'and objects.  In fact, the internal code for an interface
                                       'in CLASS A may be entirely different from the internal code
  Interface IAnimal : Inherit IUnknown 'for the same interface in CLASS B.  Method names, para-
    Property Get ItsName() As String   'meters, and return values must be identical, but the
      Property=m_strName               'internal code could  vary significantly".
    End Property

    Property Set ItsName(Byval strName As String)
      m_strName=strName
    End Property                       'Note that this class 'Animal' is a base class some of whose
                                       'Methods are overridden in derived classes.  While in this
    Method Move() As String            'case the methods of this class are useful in and of
      Method = m_strName & " Walked Across The Farm."
    End Method                         'themselves, that is not always the case.  However, it can
                                       'be useful to have a base class to provide default behavior
    Method Eat() As String             'if a method is not implemented in a derived class.  In this
      Method = m_strName & " Ate."     'program the MakeSound() Method is implemented in the "Horse'
    End Method                         'class but not in the Sheep class.  Note the effect in the
                                       'output below.
    Method MakeSound() As String
      Method="A Girrrrrh Animal Sound!"
    End Method
  End Interface
End Class


Class Horse
  Interface IHorse : Inherit Animal, IAnimal                'This class - Horse, as well as the
    Override Property Set ItsName(Byval strName As String)  'Sheep class implement the interface
      MyBase.ItsName="The Horse"                            'ICare.  The implementation is
    End Property                                            'different here though because one
                                                            'cares for a horse somewhat differently
    Override Method Eat() As String                         'than for a sheep.  Note the use of
       Method=Me.ItsName & " Ate Some Oats."                'what is termed an implicit class
    End Method                                              'pointer - Me.  In OOP C family
                                                            'languages you'll see the use of the
    Override Method MakeSound() As String                   'term 'this'.  Its usually optional
      Method=Me.ItsName & " Made A Whinny Sound!"           'to use it but to make the code
    End Method                                              'clearer I tend to use it in places
  End Interface                                             'I really don't need t.

  Interface ICare : Inherit IUnknown                        'Note that this code won't compile
    Method Groom() As String                                'without the 'Override' term in front
      Method="You Brush The Horse."                         'of the three overridden Methods.  You
    End Method                                              'don't have to provide an override for
                                                            'all the methods in the base class.
    Method Deworm() As String                               'Here though, we overrode the Annimal
      Method="You Give The Horse A Dose Of Dewormer."       'MakeSound() Method.
    End Method
  End Interface
End Class


Class Sheep
  Interface ISheep : Inherit Animal, IAnimal                'Note that in this 'Sheep' class we
    Override Property Set ItsName(Byval strName As String)  'didn't provide a unique and specific
      MyBase.ItsName="The Sheep"                            'Override for the base class MakeSound()
    End Property                                            'Method, so if MakeSound() is called on
                                                            'a Sheep object the base class method
    Override Method Eat() As String                         'will be called (see output below).
       Method=MyBase.ItsName & " Ate Some Grass."
    End Method
  End Interface

  Interface ICare : Inherit IUnknown
    Method Groom() As String
      Method="You Shear The Sheep."
    End Method

    Method Deworm() As String
      Method="You Give The Sheep A Dose Of Dewormer."
    End Method
  End Interface
End Class


Function PBMain()
  Local a_animal As IAnimal
  Local a_horse As IHorse, horse_care As ICare
  Local a_sheep As ISheep, sheep_care As ICare

  Let a_animal = Class "Animal"
  a_animal.ItsName="The Animal"
  Print a_animal.ItsName
  Print a_animal.Move()
  Print a_animal.Eat()
  Print a_animal.MakeSound()
  Print
  Let a_horse = Class "Horse"  : Let horse_care = Class "Horse"
  a_horse.ItsName="The Horse"
  Print a_horse.ItsName
  Print a_horse.Move()
  Print a_horse.Eat()
  Print a_horse.MakeSound()
  Print horse_care.Groom()
  Print horse_care.Deworm()
  Print
  Let a_sheep = Class "Sheep" : Let sheep_care = Class "Sheep"
  a_sheep.ItsName="The Sheep"
  Print a_sheep.ItsName
  Print a_sheep.Move()
  Print a_sheep.Eat()
  Print a_sheep.MakeSound()
  Print sheep_care.Groom()
  Print sheep_care.Deworm()
  Waitkey$

  PBMain=0
End Function

'Output:
'========================================
'The Animal
'The Animal Walked Across The Farm.
'The Animal Ate.
'A Girrrrrh Animal Sound!
'
'The Horse
'The Horse Walked Across The Farm.
'The Horse Ate Some Oats.
'The Horse Made A Whinny Sound!
'You Brush The Horse.
'You Give The Horse A Dose Of Dewormer.
'
'The Sheep
'The Sheep Walked Across The Farm.
'The Sheep Ate Some Grass.
'A Girrrrrh Animal Sound!
'You Shear The Sheep.
'You Give The Sheep A Dose Of Dewormer.

Below is the same program In PowerBASIC Windows 9.0

#Compile Exe    'PowerBASIC Windows Compiler 9.0
#Include "Win32api.inc"

Type WndEventArgs
  wParam As Long
  lParam As Long
  hWnd   As Dword
  hInst  As Dword
End Type

Declare Function FnPtr(wea As WndEventArgs) As Long

Type MessageHandler
  wMessage As Long
  dwFnPtr As Dword
End Type
Global MsgHdlr() As MessageHandler

Interface ICare : Inherit IUnknown     'According to Mr. Zale, an interface is a "set of methods
  Method Groom() As String             'and properties which are implemented on an object.  You
  Method Deworm() As String            'might think of it as a list of DECLARE statements where
End Interface                          'the sequence of the Declares must be preserved.  Remember,
                                       'the interface is just the definition, not the actual code.
                                       '...An interesting note is that one particular interface
Class Animal                           'definition may become a part of several different classes
  Instance m_strName As String         'and objects.  In fact, the internal code for an interface
                                       'in CLASS A may be entirely different from the internal code
  Interface IAnimal : Inherit IUnknown 'for the same interface in CLASS B.  Method names, para-
    Property Get ItsName() As String   'meters, and return values must be identical, but the
      Property=m_strName               'internal code could  vary significantly".
    End Property

    Property Set ItsName(Byval strName As String)
      m_strName=strName
    End Property                       'Note that this class 'Animal' is a base class some of whose
                                       'Methods are overridden in derived classes.  While in this
    Method Move() As String            'case the methods of this class are useful in and of
      Method = m_strName & " Walked Across The Farm."
    End Method                         'themselves, that is not always the case.  However, it can
                                       'be useful to have a base class to provide default behavior
    Method Eat() As String             'if a method is not implemented in a derived class.  In this
      Method = m_strName & " Ate."     'program the MakeSound() Method is implemented in the "Horse'
    End Method                         'class but not in the Sheep class.  Note the effect in the
                                       'output below.
    Method MakeSound() As String
      Method="A Girrrrrh Animal Sound!"
    End Method
  End Interface
End Class


Class Horse
  Interface IHorse : Inherit Animal, IAnimal                'This class - Horse, as well as the
    Override Property Set ItsName(Byval strName As String)  'Sheep class implement the interface
      MyBase.ItsName="The Horse"                            'ICare.  The implementation is
    End Property                                            'different here though because one
                                                            'cares for a horse somewhat differently
    Override Method Eat() As String                         'than for a sheep.  Note the use of
       Method=Me.ItsName & " Ate Some Oats."                'what is termed an implicit class
    End Method                                              'pointer - Me.  In OOP C family
                                                            'languages you'll see the use of the
    Override Method MakeSound() As String                   'term 'this'.  Its usually optional
      Method=Me.ItsName & " Made A Whinny Sound!"           'to use it but to make the code
    End Method                                              'clearer I tend to use it in places
  End Interface                                             'I really don't need t.

  Interface ICare : Inherit IUnknown                        'Note that this code won't compile
    Method Groom() As String                                'without the 'Override' term in front
      Method="You Brush The Horse."                         'of the three overridden Methods.  You
    End Method                                              'don't have to provide an override for
                                                            'all the methods in the base class.
    Method Deworm() As String                               'Here though, we overrode the Annimal
      Method="You Give The Horse A Dose Of Dewormer."       'MakeSound() Method.
    End Method
  End Interface
End Class


Class Sheep
  Interface ISheep : Inherit Animal, IAnimal                'Note that in this 'Sheep' class we
    Override Property Set ItsName(Byval strName As String)  'didn't provide a unique and specific
      MyBase.ItsName="The Sheep"                            'Override for the base class MakeSound()
    End Property                                            'Method, so if MakeSound() is called on
                                                            'a Sheep object the base class method
    Override Method Eat() As String                         'will be called (see output below).
       Method=MyBase.ItsName & " Ate Some Grass."
    End Method
  End Interface

  Interface ICare : Inherit IUnknown
    Method Groom() As String
      Method="You Shear The Sheep."
    End Method

    Method Deworm() As String
      Method="You Give The Sheep A Dose Of Dewormer."
    End Method
  End Interface
End Class


Function fnWndProc_OnPaint(pea As WndEventArgs) As Long
  Local a_animal As IAnimal
  Local a_horse As IHorse, horse_care As ICare
  Local a_sheep As ISheep, sheep_care As ICare
  Local lpPaint As PAINTSTRUCT
  Local hDC As Long

  hDC=BeginPaint(pea.hWnd,lpPaint)
  Let a_animal = Class "Animal"
  a_animal.ItsName="The Animal"
  Call TextOut(hDC,0,0,a_animal.ItsName,Len(a_animal.ItsName))
  Call TextOut(hDC,0,15,a_animal.Move(),Len(a_animal.Move()))
  Call TextOut(hDC,0,30,a_animal.Eat(),Len(a_animal.Eat()))
  Call TextOut(hDC,0,45,a_animal.MakeSound(),Len(a_animal.MakeSound()))
  Let a_horse = Class "Horse"  : Let horse_care = Class "Horse"
  a_horse.ItsName="The Horse"
  Call TextOut(hDC,0,75,a_horse.ItsName,Len(a_horse.ItsName))
  Call TextOut(hDC,0,90,a_horse.Move(),Len(a_horse.Move()))
  Call TextOut(hDC,0,105,a_horse.Eat(),Len(a_horse.Eat()))
  Call TextOut(hDC,0,120,a_horse.MakeSound(),Len(a_horse.MakeSound()))
  Call TextOut(hDC,0,135,horse_care.Groom(),Len(horse_care.Groom()))
  Call TextOut(hDC,0,150,horse_care.Deworm(),Len(horse_care.Deworm()))
  Let a_sheep = Class "Sheep" : Let sheep_care = Class "Sheep"
  a_sheep.ItsName="The Sheep"
  Call TextOut(hDC,0,180,a_sheep.ItsName,Len(a_sheep.ItsName))
  Call TextOut(hDC,0,195,a_sheep.Move(),Len(a_sheep.Move()))
  Call TextOut(hDC,0,210,a_sheep.Eat(),Len(a_sheep.Eat()))
  Call TextOut(hDC,0,225,a_sheep.MakeSound(),Len(a_sheep.MakeSound()))
  Call TextOut(hDC,0,240,sheep_care.Groom(),Len(sheep_care.Groom()))
  Call TextOut(hDC,0,255,sheep_care.Deworm(),Len(sheep_care.Deworm()))
  Call EndPaint(pea.hWnd,lpPaint)

  fnWndProc_OnPaint=0
End Function


Function fnWndProc_OnClose(wea As WndEventArgs) As Long
  Call PostQuitMessage(0)
  fnWndProc_OnClose=0
End Function


Function fnWndProc(ByVal hWnd As Long,ByVal wMsg As Long,ByVal wParam As Long,ByVal lParam As Long) As Long
  Register i As Long

  For i=0 To 1
    If wMsg=MsgHdlr(i).wMessage Then
       Local wea As WndEventArgs
       Local iReturn As Long
       wea.hWnd=hWnd: wea.wParam=wParam: wea.lParam=lParam
       Call Dword MsgHdlr(i).dwFnPtr Using FnPtr(wea) To iReturn
       fnWndProc=iReturn
       Exit Function
    End If
  Next i

  fnWndProc=DefWindowProc(hWnd,wMsg,wParam,lParam)
End Function


Sub AttachMessageHandlers()
  ReDim MsgHdlr(1) As MessageHandler   'Associate Windows Message With Message Handlers
  MsgHdlr(0).wMessage=%WM_PAINT    :   MsgHdlr(0).dwFnPtr=CodePtr(fnWndProc_OnPaint)
  MsgHdlr(1).wMessage=%WM_CLOSE    :   MsgHdlr(1).dwFnPtr=CodePtr(fnWndProc_OnClose)
End Sub


Function WinMain(ByVal hIns As Long,ByVal hPrev As Long,ByVal lpCL As Asciiz Ptr,ByVal iShow As Long) As Long
  Local hWnd As Dword
  Local winclass As WndClassEx
  Local szAppName As Asciiz * 16
  Local Msg As tagMsg

  szAppName="Animals"
  Call AttachMessageHandlers()
  winclass.cbSize=SizeOf(winclass)
  winclass.style=%CS_HREDRAW Or %CS_VREDRAW
  winclass.lpfnWndProc=CodePtr(fnWndProc)
  winclass.cbClsExtra=0
  winclass.cbWndExtra=0
  winclass.hInstance=hIns
  winclass.hIcon=LoadIcon(%NULL, ByVal %IDI_APPLICATION)
  winclass.hCursor=LoadCursor(%NULL, ByVal %IDC_ARROW)
  winclass.hbrBackground=GetStockObject(%WHITE_BRUSH)
  winclass.lpszMenuName=%NULL
  winclass.lpszClassName=VarPtr(szAppName)
  winclass.hIconSm=LoadIcon(hIns, ByVal %IDI_APPLICATION)
  RegisterClassEx winclass
  hWnd=CreateWindowEx(0,szAppName,"Old McDonnald Had A Farm...",%WS_OVERLAPPEDWINDOW,200,100,345,320,0,0,hIns,ByVal 0)
  Call ShowWindow(hWnd,iShow)
  While GetMessage(Msg,%NULL,0,0)
    TranslateMessage Msg
    DispatchMessage Msg
  Wend

  Function=msg.wParam
End Function

Here is the vb.net program along with command line compilation string that I'm trying to translate. Not sure of everything yet. Just feeling my way! I should give propper credit for the below program that I implemented in the above two PowerBASIC programs. I got the idea from a book I have by Mike Gunderloy on VB.NET and ADO.NET. In that book he used Visual Studio to create a Windows program where the output went into a listbox. I redid the program somewhat but just did command line compilation using Notepad to write the program in VB.NET. Below is the program. If you have the .NET runtime on your machine (you probably do) you can compile this at the command prompt. The vb.net compiler is vbc.exe and your PATHs are probably set to its location. Change vbAnimal.txt to Animal.vb.

'vb.net program.  this is a GUI output program.  Below is command line compile
'string for anyone with .NET runtime installed.  just open command line window and paste the string in starting with 'vbc'
'vbc /r:System.dll,System.Drawing.dll,System.Windows.Forms.dll /t:winexe Animal.vb
Imports System
Imports System.Drawing
Imports System.Windows.Forms

Interface Care
  Function Groom() As String
  Function Deworm() As String
End Interface


Public Class Animal
  Private mstrName As String
  
  Public Property Name() As String
    Get
      Name = mstrName
    End Get

    Set(ByVal Value As String)
      mstrName = Value
    End Set
  End Property

  Public Function Move() As String
    Move = mstrName & " Walked Across The Farm."
  End Function

  Overridable Function Eat() As String
    Eat = mstrName & " Ate."
  End Function
End Class


Public Class Horse
  Inherits Animal
  Implements Care

  Sub New()
    MyBase.Name = "The Horse"
  End Sub

  Overrides Function Eat() As String
    Eat = MyBase.Name & " Ate Some Oats."
  End Function

  Function Groom() As String Implements Care.groom
    Groom = "You Brush The Horse."
  End Function

  Function Deworm() As String Implements Care.Deworm
    Deworm = "You Give The Horse A Dose Of Dewormer."
  End Function
End Class


Public Class Sheep
  Inherits Animal
  Implements Care

  Sub New()
    MyBase.Name = "The Sheep"
  End Sub

  Overrides Function Eat() As String
    Eat = MyBase.Name & " Ate Some Grass."
  End Function

  Function Groom() As String Implements Care.groom
    Groom = "You Shear The Sheep."
  End Function

  Function Deworm() As String Implements Care.Deworm
    Deworm = "You Give The Sheep A Dose Of Dewormer."
  End Function
End Class


Class frmMain
  Inherits Form

  Sub New()
    Me.Text = "A Walk About The Farm"
    Me.BackColor = SystemColors.Window
    Me.ForeColor = SystemColors.WindowText
  End Sub

  Protected Overrides Sub OnPaint(pea As PaintEventArgs)
    Dim a As New Animal
    Dim h As New Horse
    Dim s As New Sheep
    Dim br As Brush

    br = new SolidBrush(Me.ForeColor)
    a.Name="The Animal"
    pea.Graphics.DrawString(a.Name,Me.Font,br,0,0)        'animal
    pea.Graphics.DrawString(a.Move(),Me.Font,br,0,15)     'animal
    pea.Graphics.DrawString(a.Eat(),Me.Font,br,0,30)      'animal
    pea.Graphics.DrawString(h.Move(),Me.Font,br,0,60)     'horse
    pea.Graphics.DrawString(h.Eat(),Me.Font,br,0,75)      'horse
    pea.Graphics.DrawString(h.Groom(),Me.Font,br,0,90)    'horse
    pea.Graphics.DrawString(h.Deworm(),Me.Font,br,0,105)  'horse
    pea.Graphics.DrawString(s.Move(),Me.Font,br,0,135)    'sheep
    pea.Graphics.DrawString(s.Eat(),Me.Font,br,0,150)     'sheep
    pea.Graphics.DrawString(s.Groom(),Me.Font,br,0,165)   'sheep
    pea.Graphics.DrawString(s.Deworm(),Me.Font,br,0,180)  'sheep
  End Sub
End Class


Module MainModule
  Public Sub Main()
    Application.Run(new frmMain())
  End Sub
End Module

[John Strasser]

Technically, animals don't have to move.

I believe the true defining characteristic is that they don't make their own food. They have to get it from the environment (something other than light).

<smile>

JS

[Fred Harris]

Some Animals Don't Move!

Technically, animals don't have to move.

I stand corrected, and shall defer to your superior taxonomic knowledge!

I’d think an animal that didn’t move would be sort of a protoplasmic blob. Therefore, I’ve injected a base class of ‘Blob’ before all the others from which ‘MovableAnimal’, “Horse’, and ‘Sheep’ inherit. The output from the modified program is as follows…

An Immovable Blob
I Can't Move!  I'm Just An An Immovable Blob!
Bring Me Something To Eat!  I Can't Move!  I'm Just An Immovable Blob!
I'm A Talking Immovable Blob!

A Movable Animal
Since I'm A Movable Animal, I Can Scurry/Slither/Fly About(as the case may be) In Search Of Food!
A Movable Animal Moved About And Ate Whatever It Is That Movable Animals Eat!
A Movable Animal Made a Moving Animal Sound

A Running Horse
A Running Horse Can Run Across The Prairie!
A Running Horse Ate Some Oats As It Moved About Across The Prairie.
A Running Horse Made A Whinny Sound As It Ran!
You Brush The Horse.
You Give The Horse A Dose Of Dewormer.

The Sheep
The Sheep Can Amble About Eating Grass!
The Sheep Ate Some Grass.
The Sheep Went Baaaaaah!
You Shear The Sheep.
You Give The Sheep A Dose Of Dewormer.

Here is the modified code...

#Compile Exe
#Dim All

Interface ICare : Inherit IUnknown
  Method Groom() As String
  Method Deworm() As String
End Interface


Class Blob
  Instance m_strName As String

  Interface IBlob : Inherit IUnknown
    Property Get ItsName() As String
      Property=m_strName
    End Property

    Property Set ItsName(Byval strName As String)
      m_strName=strName
    End Property

    Method Move() As String
      Method = "I Can't Move!  I'm Just An " & m_strName & "!"
    End Method

    Method Eat() As String
      Method = "Bring Me Something To Eat!  I Can't Move!" & "  I'm Just " & m_strName & "!"
    End Method

    Method MakeSound() As String
      Method="I'm A Talking Immovable Blob!"
    End Method
  End Interface
End Class


Class MovableAnimal
  Interface IMovableAnimal : Inherit Blob, IBlob
    Override Property Set ItsName(Byval strName As String)
      MyBase.ItsName=strName
    End Property

    Override Method Move() As String
      Method="Since I'm " & Me.ItsName() & ", I Can Scurry/Slither/Fly About" & _
      "(as the case may be) In Search Of Food!"
    End Method

    Override Method Eat() As String
       Method=Me.ItsName & " Moved About And Ate Whatever It Is That Movable Animals Eat!"
    End Method

    Override Method MakeSound() As String
      Method=Me.ItsName & " Made a Moving Animal Sound"
    End Method
  End Interface
End Class


Class Horse
  Interface IHorse : Inherit MovableAnimal, IMovableAnimal
    Override Property Set ItsName(Byval strName As String)
      MyBase.ItsName=strName
    End Property

    Override Method Move() As String
      Method=Me.ItsName() & " Can Run Across The Prairie!"
    End Method

    Override Method Eat() As String
       Method=Me.ItsName & " Ate Some Oats As It Moved About Across The Prairie."
    End Method

    Override Method MakeSound() As String
      Method=Me.ItsName & " Made A Whinny Sound As It Ran!"
    End Method
  End Interface
  
  Interface ICare : Inherit IUnknown
    Method Groom() As String
      Method="You Brush The Horse."
    End Method
                                                            
    Method Deworm() As String
      Method="You Give The Horse A Dose Of Dewormer."
    End Method
  End Interface
End Class


Class Sheep
  Interface ISheep : Inherit MovableAnimal, IMovableAnimal
    Override Property Set ItsName(Byval strName As String)
      MyBase.ItsName=strName
    End Property
    
    Override Method Move() As String
      Method=Me.ItsName() & " Can Amble About Eating Grass!"
    End Method
                                                                           
    Override Method Eat() As String
       Method=MyBase.ItsName & " Ate Some Grass."
    End Method
    
    Override Method MakeSound() As String
      Method=Me.ItsName & " Went Baaaaaah!"
    End Method
  End Interface

  Interface ICare : Inherit IUnknown
    Method Groom() As String
      Method="You Shear The Sheep."
    End Method

    Method Deworm() As String
      Method="You Give The Sheep A Dose Of Dewormer."
    End Method
  End Interface
End Class


Function PBMain() As Long
  Local a_blob As IBlob
  Local a_movable_animal As IMovableAnimal
  Local a_horse As IHorse, horse_care As ICare
  Local a_sheep As ISheep, sheep_care As ICare
  
  Console Set Screen 25,100
  Let a_blob = Class "Blob"
  a_blob.ItsName="An Immovable Blob"
  Print a_blob.ItsName()
  Print a_blob.Move()
  Print a_blob.Eat()
  Print a_blob.MakeSound()
  Print

  Let a_movable_animal = Class "MovableAnimal"
  a_movable_animal.ItsName="A Movable Animal"
  Print a_movable_animal.ItsName()
  Print a_movable_animal.Move()
  Print a_movable_animal.Eat()
  Print a_movable_animal.MakeSound()
  Print

  Let a_horse = Class "Horse"
  a_horse.ItsName="A Running Horse"
  Print a_horse.ItsName()
  Print a_horse.Move()
  Print a_horse.Eat()
  Print a_horse.MakeSound()
  Let horse_care = Class "Horse"
  Print horse_care.Groom()
  Print horse_care.Deworm()
  Print
  
  Let a_sheep = Class "Sheep" : Let sheep_care = Class "Sheep"
  a_sheep.ItsName="The Sheep"
  Print a_sheep.ItsName
  Print a_sheep.Move()
  Print a_sheep.Eat()
  Print a_sheep.MakeSound()
  Print sheep_care.Groom()
  Print sheep_care.Deworm()
  Waitkey$

  PBMain=0
End Function

[Jim Fritts]

Modified for PBWIN10.04 works with J. Roca includes. Thank you Fred!

#COMPILE EXE
#DIM ALL
'Fred Harris on 18 AUG 2008
'https://forum.powerbasic.com/forum/user-to-user-discussions/source-code/39206-old-mcdonnald-had-a-farm-e-i-e-i-_-o?p=456128#post456128

INTERFACE ICare : INHERIT IUNKNOWN
  METHOD Groom() AS STRING
  METHOD Deworm() AS STRING
END INTERFACE


CLASS Blob
  INSTANCE m_strName AS STRING

  INTERFACE IBlob : INHERIT IUNKNOWN
    PROPERTY GET ItsName() AS STRING
      PROPERTY=m_strName
    END PROPERTY

    PROPERTY SET ItsName(BYVAL strName AS STRING)
      m_strName=strName
    END PROPERTY

    METHOD Move() AS STRING
      METHOD = "I Can't Move!  I'm Just An " & m_strName & "!"
    END METHOD

    METHOD Eat() AS STRING
      METHOD = "Bring Me Something To Eat!  I Can't Move!" & "  I'm Just " & m_strName & "!"
    END METHOD

    METHOD MakeSound() AS STRING
      METHOD="I'm A Talking Immovable Blob!"
    END METHOD
  END INTERFACE
END CLASS


CLASS MovableAnimal
  INTERFACE IMovableAnimal : INHERIT Blob, IBlob
    OVERRIDE PROPERTY SET ItsName(BYVAL strName AS STRING)
      MyBase.ItsName=strName
    END PROPERTY

    OVERRIDE METHOD Move() AS STRING
      METHOD="Since I'm " & Me.ItsName() & ", I Can Scurry/Slither/Fly About" & _
      "(as the case may be) In Search Of Food!"
    END METHOD

    OVERRIDE METHOD Eat() AS STRING
       METHOD=Me.ItsName & " Moved About And Ate Whatever It Is That Movable Animals Eat!"
    END METHOD

    OVERRIDE METHOD MakeSound() AS STRING
      METHOD=Me.ItsName & " Made a Moving Animal Sound"
    END METHOD
  END INTERFACE
END CLASS


CLASS Horse
  INTERFACE IHorse : INHERIT MovableAnimal, IMovableAnimal
    OVERRIDE PROPERTY SET ItsName(BYVAL strName AS STRING)
      MyBase.ItsName=strName
    END PROPERTY

    OVERRIDE METHOD Move() AS STRING
      METHOD=Me.ItsName() & " Can Run Across The Prairie!"
    END METHOD

    OVERRIDE METHOD Eat() AS STRING
       METHOD=Me.ItsName & " Ate Some Oats As It Moved About Across The Prairie."
    END METHOD

    OVERRIDE METHOD MakeSound() AS STRING
      METHOD=Me.ItsName & " Made A Whinny Sound As It Ran!"
    END METHOD
  END INTERFACE

  INTERFACE ICare : INHERIT IUNKNOWN
    METHOD Groom() AS STRING
      METHOD="You Brush The Horse."
    END METHOD

    METHOD Deworm() AS STRING
      METHOD="You Give The Horse A Dose Of Dewormer."
    END METHOD
  END INTERFACE
END CLASS


CLASS Sheep
  INTERFACE ISheep : INHERIT MovableAnimal, IMovableAnimal
    OVERRIDE PROPERTY SET ItsName(BYVAL strName AS STRING)
      MyBase.ItsName=strName
    END PROPERTY

    OVERRIDE METHOD Move() AS STRING
      METHOD=Me.ItsName() & " Can Amble About Eating Grass!"
    END METHOD

    OVERRIDE METHOD Eat() AS STRING
       METHOD=MyBase.ItsName & " Ate Some Grass."
    END METHOD

    OVERRIDE METHOD MakeSound() AS STRING
      METHOD=Me.ItsName & " Went Baaaaaah!"
    END METHOD
  END INTERFACE

  INTERFACE ICare : INHERIT IUNKNOWN
    METHOD Groom() AS STRING
      METHOD="You Shear The Sheep."
    END METHOD

    METHOD Deworm() AS STRING
      METHOD="You Give The Sheep A Dose Of Dewormer."
    END METHOD
  END INTERFACE
END CLASS


FUNCTION PBMAIN() AS LONG
  LOCAL a_blob AS IBlob
  LOCAL a_movable_animal AS IMovableAnimal
  LOCAL a_horse AS IHorse, horse_care AS ICare
  LOCAL a_sheep AS ISheep, sheep_care AS ICare
  LOCAL ePrint AS STRING

  'Console Set Screen 25,100
  LET a_blob = CLASS "Blob"
  a_blob.ItsName="An Immovable Blob"
  ePrint = ePrint & a_blob.ItsName() & $CRLF
  ePrint = ePrint & a_blob.Move() & $CRLF
  ePrint = ePrint & a_blob.Eat() & $CRLF
  ePrint = ePrint & a_blob.MakeSound() & $CRLF
  ePrint = ePrint & $CRLF

  LET a_movable_animal = CLASS "MovableAnimal"
  a_movable_animal.ItsName="A Movable Animal"
  ePrint = ePrint & a_movable_animal.ItsName() & $CRLF
  ePrint = ePrint & a_movable_animal.Move() & $CRLF
  ePrint = ePrint & a_movable_animal.Eat() & $CRLF
  ePrint = ePrint & a_movable_animal.MakeSound() & $CRLF
  ePrint = ePrint & $CRLF

  LET a_horse = CLASS "Horse"
  a_horse.ItsName="A Running Horse"
  ePrint = ePrint & a_horse.ItsName() & $CRLF
  ePrint = ePrint & a_horse.Move() & $CRLF
  ePrint = ePrint & a_horse.Eat() & $CRLF
  ePrint = ePrint & a_horse.MakeSound() & $CRLF
  LET horse_care = CLASS "Horse"
  ePrint = ePrint & horse_care.Groom() & $CRLF
  ePrint = ePrint & horse_care.Deworm() & $CRLF
  ePrint = ePrint & $CRLF

  LET a_sheep = CLASS "Sheep" : LET sheep_care = CLASS "Sheep"
  a_sheep.ItsName="The Sheep"
  ePrint = ePrint & a_sheep.ItsName & $CRLF
  ePrint = ePrint & a_sheep.Move() & $CRLF
  ePrint = ePrint & a_sheep.Eat() & $CRLF
  ePrint = ePrint & a_sheep.MakeSound() & $CRLF
  ePrint = ePrint & sheep_care.Groom() & $CRLF
  ePrint = ePrint & sheep_care.Deworm() & $CRLF
  ePrint = ePrint & $CRLF

  ? ePrint

  'Waitkey$

  PBMAIN=0
END FUNCTION