Despite its simplicity, there are some disadvantages to the RubyCocoa approach:

• Importing the class is ugly. Instead of simply require ‘jukebox’, we must also import the RubyCocoa bridge (require ‘osx/cocoa’) and then explicitly import our jukebox class using OSX::ns_import :Jukebox. If you want, you can hide this in a Ruby module that does the importing behind the scenes. But for me, the objective is to write as little glue code as possible, so I can live with a little discomfort here.

• We have to use RubyCocoa/Objective-C object allocation and initialization. Instead of calling Jukebox.new to create our jukebox objects, we have to perform the standard Objective-C two step initialization. First call alloc, then the init function, in this case initWithUnit.

• If you work through the example in Programming Ruby, you’ll see Dave Thomas illustrate a way to pass a block into the jukebox seek function. The seek function then calls that block back to report progress. This is not (yet?) possible with RubyCocoa. I’ve dug around a bit in the RubyCocoa source code and didn’t find anything that seemed to wrap blocks. So if you need that capability, you have to use the C-level interface.

• The RubyCocoa bridge code is undoubtably slower than a custom-coded C extension. To me, that’s not a big issue. It would only be a problem if I’m calling across the boundary a lot, and if I am, then I’d want to reorganize my code to make those calls from Objective-C. Not messing with glue code gives me more time to do that.

Now let’s consider the advantages of writing Ruby extensions with RubyCocoa:

• You can call the exact same interface from Objective-C. “Wait,” you say, “I could have called my original interface from Objective-C!” True, but for a non-trivial example, writing that Objective-C wrapper will probably force you to clean up your interface a bit as well (ask a QuickTime programmer about this!). And hey, now your slithery friends can also use your code from Python with PyObjC.

• It only works on a Mac. “Wait”, you say again, “isn’t that a disadvantage?” Yes, but do you really need any more excuses to switch?

• It is really really really simple. If you need to make the comparison for yourself, the corresponding C code is in the pickaxe book on pages 290-293 (the Extending Ruby chapter runs from pages 275-314).

Thanks for reading! If you have any comments or suggestions, please send them to me at the link below.

Tim Burks