Le 26 mai 2010 à 15:10, vincent habchi a écrit : > Le 26 mai 2010 à 14:53, Graham Cox a écrit : > >> >> On 26/05/2010, at 10:41 PM, vincent habchi wrote: >> >>> Hmmm... Let's say you have a class A with a private variable "priv" and b a >>> pointer to a subclass of A. Is: >>> >>> [(A *)b priv] >>> >>> legal? >> >> >> No. It's not legal syntax for accessing an ivar in any case - square >> brackets invoke a method:- [instance method]. > > Granted. I assumed there was a getter defined. That's because, AFAIC, I > almost always synthesize ivars, so they become regular attributes. > >> Perhaps you could ask is: >> >> (A*)b->priv legal? > > Yes. Indeed. > >> Depends. If priv is @private it is invisible to code other than within the >> methods of class A itself, so if this code lived inside such a method it >> would work, otherwise it would not. I don't think the cast makes any >> difference. > > So, tell me if I'm wrong, but I infer from your answer that whatever I can > do, there is no means for a subclass A' to access any private variable of its > ancestor. > >> But this is not getting to the problem that the OP is having, which AFAICS >> is unrelated to @private. @private is a Good Thing™ - often worth using. > > Well, as a regular Python code writer, I've never missed @private (or even > @protected) declarations. I fail anyhow to grasp the relevancy of @private > vis-à-vis @protected: It seems logical to me that subclasses be granted > access to all ancestor attributes.
Why a subclass should have more right to mess up with private ivar than an external class ? Who knows what a class does when you set an ivar using the accessor. It would badly break encapsulation principle. For example, what would append if a NSView subclass change the view frame by accessing the _frame ivar directly ? -- Jean-Daniel _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
