unterschiedliche Klassen variabel instanzieren

[Bjoerk]

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Delphi-Quellcode:

unit Unit1;

interface

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

type
  TKlasse = class(TObject)
  public
    constructor Create(const ATyp: integer); overload;
    constructor Create; overload;
  end;

  TKlasse1 = class(TKlasse)
    function MachWas: string;
  end;

  TKlasse2 = class(TKlasse)
    function MachWas: string;
  end;

  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Machwas(const ATyp:integer);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  Machwas(1);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Machwas(2);
end;

procedure TForm1.Machwas(const ATyp:integer);
var
  Klasse: TKlasse;
begin
  if ATyp=1 then
  begin
    Klasse:=TKlasse.Create(ATyp);
    try
      with Klasse as TKlasse1 do ShowMessage(Machwas);
    finally
      Klasse.Free;
    end;
  end;
  if ATyp=2 then
  begin
    Klasse:=TKlasse.Create(ATyp);
    try
      with Klasse as TKlasse2 do ShowMessage(Machwas);
    finally
      Klasse.Free;
    end;
  end;
end;

constructor TKlasse.Create;
begin
  inherited Create;
end;

constructor TKlasse.Create(const ATyp: integer);
begin
  if ATyp=1 then Self:= TKlasse1.Create;
  if ATyp=2 then Self:= TKlasse2.Create;
end;

function TKlasse1.MachWas: string;
begin
  Result:= 'TKlasse1.MachWas';
end;

function TKlasse2.MachWas: string;
begin
  Result:= 'TKlasse2.MachWas';
end;

end.