Neue Komponente von bestehender ableiten

[SirThornberry]

also ich würde das ganze so lösen:

Delphi-Quellcode:

  TIntEdit = class(TEdit)
  private
    fAllowed: String;
    fNewOnChange: TNotifyEvent;
    fNewOnKeyPress: TKeyPressEvent;
    function fGetText: String;
    procedure fSetText(AValue: String);
    procedure fOnKeyPressproc(Sender: TObject; var Key: Char);
    procedure fOnChangeProc(Sender: TObject);
  public
    constructor Create(AOwner: TComponent); override;
  published
    property Text: String read fGetText write fSetText;
    property OnChange: TNotifyEvent read fNewOnChange write fNewOnChange;
    property OnKeyPress: TKeyPressEvent read fNewOnKeyPress write fNewOnKeyPress;
  end;

[...]

constructor TIntEdit.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  fAllowed := '0123456789';
  inherited OnKeyPress := fOnKeyPressproc;
  inherited OnChange := fOnChangeProc;
end;

function TIntEdit.fGetText: String;
begin
  result := inherited Text;
end;

procedure TIntEdit.fSetText(AValue: String);
var LCount: Integer;
begin
  for LCount := 1 to length(AValue) do
  begin
    if pos(AValue[LCount], fAllowed) > 0 then Exit;
  end;
  inherited Text := AValue;
end;

procedure TIntEdit.fOnKeyPressproc(Sender: TObject; var Key: Char);
begin
  if pos(key, fAllowed) < 1 then
     key := #0
  else if Assigned(fNewOnKeyPress) then fNewOnKeyPress(Sender, Key);
end;

procedure TIntEdit.fOnChangeProc(Sender: TObject);
var LCount: Integer;
    Lnew: String;
begin
  LNew := '';
  for LCount := 1 to length(Text) do
  begin
    if pos(Text[LCount], fAllowed) > 0 then
       LNew := LNew + Text[LCount];
  end;
  if LNew <> Text then Text := LNew;
  if Assigned(fNewOnChange) then fNewOnChange(Sender);
end;

Wobei diese Variante kein "Strg + V" mehr zulässt