Re: class/subclass ivars

[David Chisnall]

If the ivars are declared in the @interface, then they are visible to all 
subclasses and you will get an error if the names match ones declared in 
subclasses.  If the ivars are declared in the @implementation context, then you 
will get no error and each class will refer to its own private version.  This 
gets a bit complicated when you refer to the ivars by name in introspection 
(you’ll likely see confusing things if you tell KVC to directly access ivars, 
for example).

David

> On 11 Jan 2016, at 15:16, Riccardo Mottola <address@hidden> wrote:
> 
> Hi,
> 
> I have a simple question and I am unsure about the answer.
> 
> Suppose we have class A with an ivar _var.
> 
> Now, I subclass A with B. Since I don't know the declaration of A, I also 
> need an ivar and call it _var and they probably have the same type.
> 
> What happens? Do I get a compiler error? Does the compiler smartly renames 
> the two variables like _var_A and _var_B? Does the second declaration get 
> ignored and the code refers to the same variable? I would expect the  
> renaming behaviour, but the latter also makes
> 
> I wonder if there is risk calling vars like "_size" or "width" "height" which 
> have common names enough to be declared up in the hierarchy.
> I am debugging code that works on Mac and not on GS, so I got the doubt.
> 
> Riccardo
> 
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