Member Class löschen

[smallie]

Wie wär's damit, den constructor auf die Instanz anzuwenden?

Sieht zwar ungewohnt aus, hat aber den Vorteil, die Vererbungshierarchie zu berücksichtigen.

Delphi-Quellcode:

type
  TClearingClass = class
  private
  public
    s: string;
    i: integer;
    constructor create; 
  end;

  TClearingChild = class(TClearingClass)
  public
    d: double;
    constructor create;
  end;  

implementation

{ TClearingClass }

constructor TClearingClass.create;
begin
  inherited;
  // explizit:
  s := '';
  i := 0;
end;

{ TClearingChild }

constructor TClearingChild.create;
begin
  inherited;
  d := 0.0;
end;

Beispiel:

Delphi-Quellcode:

type

  TForm1 = class(TForm)
    btnCreate: TSpeedButton;
    btnInit: TSpeedButton;
    procedure btnCreateClick(Sender: TObject);
    procedure btnInitClick(Sender: TObject);
  private
  public
  end;

implementation

procedure TForm1.btnCreateClick(Sender: TObject);
begin
  ClearingChild := TClearingChild.create; //Constructor
  showMessageFmt('s: %s, i: %d, d: %g',
    [ClearingChild.s, ClearingChild.i, ClearingChild.d]);   //s: , i: 0, d: 0

end;

procedure TForm1.btnInitClick(Sender: TObject);
begin
  ClearingChild.s := 'changed';
  ClearingChild.i := -1;
  ClearingChild.d := -1.1;
  ClearingChild.create; //Instanz initialisieren
  showMessageFmt('s: %s, i: %d, d: %g',
    [ClearingChild.s, ClearingChild.i, ClearingChild.d]);   //s: , i: 0, d: 0
end;