> A C struct can't forward requests to perform a function onto other targets.
That'd be true if methods were called statically, but with dynamic linking this is no longer the case.
Also, obligatory reminder: much of the interface covered here is runtime implementation–don't mess with it! Some of the stuff mentioned is already outdated.
A lot of the information here is about the (relatively stable) hooks the objc runtime gives programmers into its internals. If you’re writing ffi code to interact with the objc runtime, a lot of the functions referenced here are reasonable to call directly in the interop layer
Objective-C 2.0 was part of 10.5 in 2007. It’s not directly tied to 64-bit support. You’re thinking of features that require the “modern runtime” which is only available on 64-bit Mac. Those features came after ObjC 2.0.
"Objective-C 2.0" was a marketing term for a bunch of features added in 10.5, some big (e.g. nonfragile ivars, garbage collection) others not so big (e.g. for..in loops, synthesized ivars). The language+runtime has evolved tremendously since then without a new marketing name. Generics and ARC were added, garbage collection and vtable dispatch have been removed.
That'd be true if methods were called statically, but with dynamic linking this is no longer the case.
Also, obligatory reminder: much of the interface covered here is runtime implementation–don't mess with it! Some of the stuff mentioned is already outdated.