
<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On 21 Dec 2010, at 00:16, Jonas Maebe wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>On 20 Dec 2010, at 21:37, Sven Barth wrote:<br><br><blockquote type="cite">- should abstract methods be forbidden?</blockquote><br>Yes, since<br>a) they are virtual<br>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)<font class="Apple-style-span" color="#000000"><font class="Apple-style-span" color="#144FAE"><br></font></font></div></blockquote><br></div><div>Actually, it seems that inheritance is in fact allowed for Delphi-style class helpers: <a href="http://qc.embarcadero.com/wc/qcmain.aspx?d=76577">http://qc.embarcadero.com/wc/qcmain.aspx?d=76577</a> (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.</div><div><br></div><div>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):</div><div>* <a href="http://docwiki.embarcadero.com/RADStudio/en/E2295_A_class_helper_cannot_introduce_a_destructor_(Delphi)">http://docwiki.embarcadero.com/RADStudio/en/E2295_A_class_helper_cannot_introduce_a_destructor_(Delphi)</a></div><div>* <a href="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/E2296_A_constructor_introduced_in_a_class_helper_must_call_the_parameterless_constructor_of_the_helped_class_as_the_first_statement_(Delphi)</a></div><div>* <a href="http://docwiki.embarcadero.com/RADStudio/en/E2358_Class_constructors_not_allowed_in_class_helpers_(Delphi)">http://docwiki.embarcadero.com/RADStudio/en/E2358_Class_constructors_not_allowed_in_class_helpers_(Delphi)</a></div><div><br></div><div><br></div><div>Jonas</div></body></html>