----- "Jonas Maebe" <[email protected]> schreef: > >
On 21 Dec 2010, at 00:16, Jonas Maebe wrote: On 20 Dec 2010, at 21:37, Sven Barth wrote: > > - should abstract methods be forbidden? > Yes, since > a) they are virtual > b) even if it were possible to have virtual methods, there would be no way to > override them with implementations that do something (since you cannot > inherit from a class helper) > > Actually, it seems that inheritance is in fact allowed for Delphi-style class helpers: http://qc.embarcadero.com/wc/qcmain.aspx?d=76577 (it's not for Objective-C categories). But I'm still quite sure you cannot do anything that requires changes to the VMT of the helped class. > There are also at some extra checks that must be added for constructors/destructors introduced via class helpers (Objective-C/Pascal doesn't have constructors or destructors, so it doesn't matter there): * http://docwiki.embarcadero.com/RADStudio/en/E2295_A_class_helper_cannot_introduce_a_destructor_(Delphi) * http://docwiki.embarcadero.com/RADStudio/en/E2296_A_constructor_introduced_in_a_class_helper_must_call_the_parameterless_constructor_of_the_helped_class_as_the_first_statement_(Delphi) * http://docwiki.embarcadero.com/RADStudio/en/E2358_Class_constructors_not_allowed_in_class_helpers_(Delphi) > hi, it seems that the virtual methods can be overridden (AOP style) using the TVirtualMethodInterceptor that comes with Delphi XE. It can also be on a per instance base (as opposed to on a per type) if I've read up on it correctly. I'd say that would be a better candidate for that purpose/intent/use case. kind regards, Dimitri Smits
_______________________________________________ fpc-devel maillist - [email protected] http://lists.freepascal.org/mailman/listinfo/fpc-devel
