Is it possible to define ivars in Objective-C extension?

Question

I wonder if it is possible to write something like this in the .m file:

@interface MyController () {//ERROR here
    Foo *privateFoo; 
}
@end

I did it but I get : Expected identifier or '{' before '{' token, I think I heard/watch a video (WWDC2010) saying this is possible or will be possible and currently only some architectures support it... but I not really sure and I cannot remember the video name.

I hope I can get some advice here.

Ignacio.

Answer 1

It is not possible to handle it this way. Categories define additional behaviour only, not state.

Answer 2

You can do this in the modern runtime (64-bit/iOS) with clang (“LLVM Compiler 1.5”) in Xcode 3.2.3 or 3.2.4, by adding -Xclang -fobjc-nonfragile-abi2 to the Other C Flags build setting. (Note that this is actually one option, not two.)

Another effect of this flag is to cause properties to be synthesized by default.