{$MODE DELPHI} // Enable Class support

type
  TFruit = Class(TObject)  // This is an actual class definition :
    // Internal class field definitions - only accessible in this unit
    private
      isRound  : Boolean;
      length   : single;
      width    : single;
      diameter : single;
    // Fields and methods only accessible by this class and descendants
    protected
    // Externally accessible fields and methods
    public
      // 2 constructors - one for round fruit, the other long fruit
      constructor Create(diameter : single);               overload;
      constructor Create(length : single; width : single); overload;
    // Externally accessible and inspectable fields and methods
    published
      // Note that properties must use different names to local defs
      property round : Boolean read isRound;
      property len   : single  read length;
      property wide  : single  read width;
      property diam  : single  read diameter;
  end;                    // End of the TFruit class definition

var
  apple, banana : TFruit;

// Create a round fruit object
constructor TFruit.Create(diameter: single);
begin
  // Indicate that we have a round fruit, and set its size
  isRound       := true;
  self.diameter := diameter;
end;

// Create a long fruit object
constructor TFruit.Create(length, width: single);
begin
  // Indicate that we have a long fruit, and set its size
  isRound     := false;
  self.length := length;
  self.width  := width;
end;

// Show what the characteristics of our fruit are
procedure ShowFruit(fruit: TFruit);
begin
  if fruit.round then Writeln('We have a round fruit, diameter = ',fruit.diam)
  else begin
    Writeln('We have a long fruit');
    Writeln('    it has length = ',fruit.len);
    Writeln('    it has width  = ',fruit.wide);
  end;
end;

Begin
  // Let us create our fruit objects
  apple  := TFruit.Create(3.5);
  banana := TFruit.Create(7.0, 1.75);

  // Show details about our fruits
  ShowFruit(apple);
  ShowFruit(banana);
end.