On 24/11/2011 05:47, Graeme Geldenhuys wrote:
On 2011-11-24 03:58, Luiz Americo Pereira Camara wrote:
possible to get the expected behavior without forcing programmer to
create a virtual constructor by using the new RTTI
What has the "new RTTI" got to do with anything?
Simply define TObj.Create as virtual, and TFoo.Create as overridden.
This is rather normal coding practise with classes. Nothing special.
This solution is not quite generic because is necessary to descend from
an specific class and also needs to change an interface declaration. So
to use in old code / classes it would be necessary to change the
hierarchy and the interface.
Also it would not work with classes that i cant change the hierarchy
like rtl ones or third party
With Delphi is possible to call a constructor even if has a different
name from Create and with parameters without changing interface or hierarchy
It seems useful for me
Luiz
----8<-------------8<-------------8<-------------8<-------------8<----
program test;
{$mode ObjFpc}{$H+}
type
TObj = class
public
constructor create; virtual;
end;
TObjClass=class of TObj;
TFoo = class(TObj)
public
constructor create; override;
end;
constructor TObj.Create;
begin
inherited create;
WriteLn('TObj.create');
end;
constructor TFoo.create;
begin
inherited Create;
WriteLn('TFoo.Create');
end;
var
cls: TObjClass;
obj: TObj;
begin
cls := TFoo;
WriteLn('cls class is ',cls.ClassName);
Obj := cls.Create;
Obj.Free;
end.
----8<-------------8<-------------8<-------------8<-------------8<----
And here is the output...
$ ./test
cls class is TFoo
TObj.create
TFoo.Create
Regards,
- Graeme -
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