Overwriting interim classes
lazarus / 21-General

----------------------------------------------------------------------
egsuh · 2022-04-11 02:53

Hi, I'm using interposing very usefully, as follows.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i unit
aqframe; interface uses   Classes, SysUtils, FileUtil, Forms,
Controls, Grids, ComCtrls;  type   TStringGrid =
class(Grids.TStringGrid)   protected      procedure KeyPress(var Key:
Char); override;      procedure EditingDone; override;      procedure
HeaderSizing(const IsColumn: Boolean;const AIndex, ASize: Integer);
override;      procedure DoPrepareCanvas(aCol, aRow: Integer; aState:
TGridDrawState); override;   public      procedure
AdjustRowHeight(ARow: Integer);      procedure AdjustRowHeights;     
procedure MoveDownRow;      procedure MoveUpRow;   end; //---------
 unit rcfeditor_6; interface uses   Classes, SysUtils, FileUtil,
Forms, Controls, ValEdit, ComCtrls, Menus,   ActnList, ExtCtrls,
StdCtrls, Buttons, CodeFrame, aqframe;   // <== here I use aqframe  
In this way, all following TStringGrid components act as I defined in
aqframe unit.

Now, I'd like to apply my default actions that I have overridden to
TValueListEditor as well.  Of course it's simple, if I make a copy of
my TStringGrid methods to TValueListEditor.

But both TStringGrid and TValueListEditor are descendants of
TCustomStringGrid, so overriding TCustomStringGrid will apply to both
components. I can't think of a neat way to do this --- will class
Helpers do this? Or is there anyway that I can override TCustomGrid's
methods, so that both TStringGrid and TValueListEditor use overriding
methods?

----------------------------------------------------------------------
Wallaby · 2022-04-11 04:43

AFAIK with a class helper you can add any methods to all
TCustomStringGrid descendants, but it's not to possible to override
methods.

There is no way to override some methods of TCustomStringGrid and tell
the compiler to use that class as ancestor for standard TStringGrid
and TValueListEditor.

You will have to duplicate code overriding methods in TStringGrid and
TValueListEditor. Non-overrides can be made with class helpers if you
want to minimise the code.