Package vs. DLL <> Plug-Ins

[Scrap]

Folgender Code liefert den Fehler bei Zeile:
MyElement.Parent := Form1; ... eine Exception der Klasse EConverError aufgetreten. Meldung; 'TFont kann nicht zu TFont zugewisen werden'.....

Wenn ich die Zeile weglasse, läuft der Code jedoch ohne das Objekt anzuzeigen.

Mein Eindruck:
Delphi geht nicht davon aus, dass beide OberKlasse dieselben sind, da an zwei Orten (DLL und Programm) deklariert und implementiert. Die Oberklassen könnten, müssen aber nicht, gleich sein.

Delphi-Quellcode:

unit programm;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

TYPE
    TOberKlasse = CLASS(TCustomControl)
    PUBLIC
       CONSTRUCTOR Create(AOwner: TComponent); OVERRIDE;
       DESTRUCTOR  Destroy; OVERRIDE;
END;

FUNCTION GetElement(MyForm : TForm):TOberKlasse;EXTERNAL 'Project2.dll';


type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

var
  Form1: TForm1;
  MyElement : TOberKlasse;

implementation
{$R *.dfm}
////////////////////////////////////////////////////////////////////////////////
// Konstruktor
CONSTRUCTOR TOberKlasse.Create(AOwner: TComponent);
BEGIN
     INHERITED Create(AOwner);
     Visible := True;
END;

////////////////////////////////////////////////////////////////////////////////
// Destruktor
DESTRUCTOR TOberKlasse.Destroy();
BEGIN
     INHERITED Destroy;
END;

procedure TForm1.Button1Click(Sender: TObject);
begin
  MyElement := GetElement(Form1);
  MyElement.Parent := Form1;
  MyElement.Top := 26;
  MyElement.Left := 10;
  MyElement.Height := 25;
  MyElement.Width := 25;
end;

end.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
DLL
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Delphi-Quellcode:

LIBRARY Project2;

uses
  SysUtils, Classes, Forms, Controls;

  {$R *.RES}

TYPE
    TOberKlasse = CLASS(TCustomControl)
    PUBLIC
       CONSTRUCTOR Create(AOwner: TComponent); OVERRIDE;
       DESTRUCTOR  Destroy; OVERRIDE;
END;

TYPE
  TUnterKlasse = CLASS(TOberKlasse)
  PUBLIC
    CONSTRUCTOR Create(AOwner: TComponent); OVERRIDE;
    DESTRUCTOR  Destroy; OVERRIDE;
END;

////////////////////////////////////////////////////////////////////////////////
// Konstruktor
CONSTRUCTOR TUnterKlasse.Create(AOwner: TComponent);
BEGIN
  INHERITED Create(AOwner);
END;

////////////////////////////////////////////////////////////////////////////////
// Destruktor
DESTRUCTOR TUnterKlasse.Destroy;
BEGIN
  INHERITED Destroy;
END;

////////////////////////////////////////////////////////////////////////////////
// Konstruktor
CONSTRUCTOR TOberKlasse.Create(AOwner: TComponent);
BEGIN
     INHERITED Create(AOwner);
     Visible := True;
END;

////////////////////////////////////////////////////////////////////////////////
// Destruktor
DESTRUCTOR TOberKlasse.Destroy();
BEGIN
     INHERITED Destroy;
END;

FUNCTION GetElement(MyForm :TForm) : TOberKlasse;
BEGIN
     result := TUnterKlasse.Create(MyForm);
END;

EXPORTS
   GetElement;

BEGIN

END.

[edit=Daniel B]Delphi-Tags gesetzt. MfG Daniel B.[/edit]