TUnicorn

program TypeClass;

uses
  Unicorn;

var
  Twilight: TUnicorn;

begin
  Twilight := TUnicorn.Create('Twilight');
  Twilight.Free;
end.

{...}

unit Pony;

interface

type
  TPony = class(TObject)
  protected
    FName: AnsiString;
  public
    constructor Create(constref AName: AnsiString);
    destructor Destroy(); override;
    procedure IntroduceSelf(); virtual; abstract;
    procedure Walk(); virtual; abstract;
  published
    property Name: AnsiString read FName;
  end;

implementation

constructor TPony.Create(constref AName: AnsiString);
begin
  FName := AName;
end;

destructor TPony.Destroy();
begin
  inherited Destroy();
end;

end.

{...}

unit Unicorn;

interface

uses
  Pony;

type
  TUnicorn = class(TPony)
  public
    procedure IntroduceSelf(); override;
    procedure Walk(); override;
  end;

implementation

procedure TUnicorn.IntroduceSelf();
begin
end;

procedure TUnicorn.Walk();
begin
end;

end.