Re: subclass overwriting superclass ivar
Re: subclass overwriting superclass ivar
- Subject: Re: subclass overwriting superclass ivar
- From: Roland King <email@hidden>
- Date: Wed, 26 May 2010 21:00:49 +0800
@interface A(MyCategory)
-(void)someMethodWhichLegallyAccessesThePrivateVariablePriv;
@end
That's legal, I can write a category against an already-compiled class without having the source and without recompiling it and I can access any of the private variables of that class. So no the compiler cannot throw away instance variables when it compiles the class originally even if no method of A used them originally because someone might go write a category against the compiled object which needs it later.
I'm sure there are other, much simpler reasons.
On 26-May-2010, at 8:41 PM, vincent habchi wrote:
> Le 26 mai 2010 à 14:22, Graham Cox a écrit :
>
>> I'm pretty sure you are mistaken. If this were even remotely true, object programming would be impossible.
>>
>> @private only declares the visibility of an ivar to its subclasses, it does not give the compiler carte blanche to write over anything it fancies.
>
> 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?
>
> Now, admitting B never accesses any of A variables, can the compiler optimize space by throwing away all A private variables?
>
> Vincent
>
> PS: thanks for this "carte blanche" :)_______________________________________________
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