Yes, MacRuby obsoletes RubyCocoa.
MacRuby (ruby 1.9+) is the future of RubyCocoa (ruby 1.8). The same developer works on both for Apple (Laurent Sansonetti). He would not be working on MacRuby if RubyCocoa had a future. When I spoke to him, I gathered that he’s looking forward to production level MacRuby so he can drop maintenance on RubyCocoa.
Ironically, the first production level release of MacRuby is slated for “2008-11” (http://www.macruby.org/trac/wiki/WhyMacRuby), the same month this book releases. This smacks of “planned obsolescence” :-).
I suggest refocusing the book on MacRuby rather than RubyCocoa. Yes, they’re similar, but MacRuby is the future of Ruby on OSX: RubyCocoa does 1.8 and prior; MacRuby does 1.9/2.0 and beyond. MacRuby is also very special compared to the cumbersome (but typical) scripting-bridged, converted, and proxied object approach that RubyCocoa takes (and all other mainstream OSX scripting languages take) to Objective-C compatibility. Why?
MacRuby makes ruby support on OSX virtually seamless with Objective-C in a way scripting bridge (typical scripting languages) can not match. I believe this book should focus its love on MacRuby and highlight its strategic advantage of ObjC compatibility (over and above OSX’s other mainstream scripting approaches, including RubyCocoa). With MacRuby, this book becomes incredibly timely.
A MacRuby focus could be the difference between an incredibly timely and great book and a just very well written (but slightly out of sync) book, and early adopters prefer timely and current books. RubyCocoa should probably become a brief appendix in the back about how to upgrade code from RubyCocoa to MacRuby (a la Jakub Suder’s primer above). So I suggest retargeting and focusing the book on MacRuby to make it fully relevant, attractive to all early adopters (your prime ruby on OSX target market), and potentially great.
Well written, timely book. Cool stuff. 2c.
P.s., Brian (and PragProg) perhaps you could contact Laurent Sansonetti (google says: lsansonetti@…) about MacRuby vs RubyCocoa and the Ruby on OSX roadmap, and even get him to write a Foreword for your book.