On 11/02/2016 17:29 μμ, Graeme Geldenhuys wrote:
Hi,
Why does TControl.AssignTo() have a special case for TCustomAction?
TCustomAction.AssignTo() already does property assignments, so what is
the reason for the special code in TControl.AssignTo?
Here is the code in question:
procedure TControl.AssignTo(Dest: TPersistent);
begin
if Dest is TCustomAction then
with TCustomAction(Dest) do begin
Enabled := Self.Enabled;
Hint := Self.Hint;
Caption := Self.Caption;
Visible := Self.Visible;
OnExecute := Self.OnClick;
HelpContext := Self.HelpContext;
HelpKeyword := Self.HelpKeyword;
HelpType := Self.HelpType;
end
else inherited AssignTo(Dest);
end;
Regards,
- Graeme -
TPersistent introduces 2 methods that help implement a data copy between
the controls. 1) the well known and mostly used Assign method where you
copy the data from an external control and 2) AssignTo method where you
write code to copy the controls values to an external control instead of
inheriting the named control. The second method gives you control over
3rd party controls that you do not and should not inherit just to code
some data copy compatibility. As an example lets assume that I'm
writting a DBGRid descendant/replacement by overriding the assign method
I allow my control to copy settings from a TDBGrid, in code that would
be MyDBGrid.Assign(DBGrid1);. Overriding the ASsignedTo method you allow
the opposite as well ee DBGrid1.Assign(MyDBGrid) will call
TMyDBGrid.AssignTo(DBGrid1) and my code will copy my internal data to
the dbgrid1.
To sum it up TControl.AssignTo code enables any TControl descendant to
be assigned to a TCustomAction, ee code like ActFileOpen.Assign(Shape1);
--
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