Re: RFC: Non-fragile ivars

[address@hidden]

On 3 Jun., 15:47, Michael Ash <m...@mikeash.com> wrote:
> Saso Kiselkov <skisel...@gmail.com> wrote:
> > It would be great to also add this algorithm into +poseAsClass: and
> > possibly category handling, since that would allow to have posing
> > classes and categories define their own ivars.
>
> You have to be really careful with this because you can't have any
> existing instances of the class in question when you make such a
> modification. If there are already objects floating around then a lot of
> bad things happen. This will work fine if you load categories at launch or
> explicitly pose before creating objects, but normally these two operations
> have been safe to perform at will. I assume that this is at least part of
> the reason why Apple doesn't allow declaring ivars in categories even with
> their new shiny runtime.
>

Ah, this may be the reason why class posing is no longer available in
Obj-C 2.0 and the new Apple Runtime (but for 64 bit mode only!)...

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/DeprecationAppendix/AppendixADeprecatedAPI.html

"Posing is deprecated in Mac OS X v10.5. The poseAsClass: method is
not available in 64-bit applications on Mac OS X v10.5."

http://developer.apple.com/releasenotes/Cocoa/RN-ObjectiveC/index.html#//apple_ref/doc/uid/TP40004309-DontLinkElementID_10

"All instance variables in 64-bit Objective-C are non-fragile."

But: where do we really need class posing (although I like the
concept)?

-- hns