Re: subclass overwriting superclass ivar
Re: subclass overwriting superclass ivar
- Subject: Re: subclass overwriting superclass ivar
- From: Jean-Daniel Dupas <email@hidden>
- Date: Wed, 26 May 2010 15:09:21 +0200
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]. Obj-C does not have the concept of private/public/protected methods, unlike C++.
>
> Perhaps you could ask is:
>
> (A*)b->priv legal?
>
> 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.
Just for the record, to be exact, @private ivar is invisible to code other than within the class A @implementation. You can access private ivars from a plain C function defined in the class A @implementation block.
> 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.
>
> --Graham
-- Jean-Daniel
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