Re: subclass overwriting superclass ivar
Re: subclass overwriting superclass ivar
- Subject: Re: subclass overwriting superclass ivar
- From: vincent habchi <email@hidden>
- Date: Wed, 26 May 2010 15:10:58 +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].
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.
Vincent_______________________________________________
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