CORBA on Mac OS X (Cocoa)

Answer 1

FWIW, I wouldn't use CORBA unless you have existing CORBA-based infrastructure you need to interface with.

CORBA was OK in its day, but it is a "dying" technology, and you are going to have a hard time getting the necessary support going forward. There is also a pretty steep learning curve.

I'd stay away from the Cocoa/Gnustep stuff too, if you want something cross-platform, as it really isn't very well supported anywhere other than OS X and iOS.

Rather than mastering these legacy technologies, I think your time would be better spent figuring out how to use Web Services, SOAP, or other mainstream cross-platform integration technologies.

Answer 2

So the easiest way to implement distributed objects in Cocoa is with, well, Distributed Objects. This really is a very straightforward way to get RMI (here's a full example). However the protocol is proprietary and can't be used with non-Apple platforms; while GNUstep does use DO and I've used their implementation successfully on cross-platform projects, their protocol is not compatible with Apple's. So you'd either have to use GNUstep in its gnu-gnu-gnu library combo on Mac OS X instead of Cocoa (which is not something I'd recommend), or choose a different approach.

So CORBA is one such "different approach". The main differences between CORBA and DO are:

• in CORBA, you define the messaging interface using IDL which is used to generate ObjC. With DO, you use Objective-C directly.
• CORBA doesn't support "duck typing"; it's strongly typed, so every method you intend to use remotely must be specified in the IDL. This also means that any method you do use is guaranteed to be implemented at the other end (of course the other end isn't guaranteed to be available in any RMI implementation).
• most of CORBA's user base isn't on ObjC (Java and C++ are more common).
• CORBA has wider platform support.
• CORBA implementations don't need to be in ObjC.