Objective-C / Cocoa target in progress
I've been spending the last few days working on an Objective-C / Cocoa target and runtime. 

https://github.com/tlindner/kaitai_struct_compiler (branch: add_objc)
https://github.com/tlindner/kaitai_struct_tests (branch: add_objc)
https://github.com/tlindner/kaitai_struct_objc_runtime

If anyone would like to comment on the work in progress I'd appreciate it.

Also, I understand a Swift target would be generally more useful, but I am not a Swift programmer. Learning Scala and all the other target languages to complete this project should lead me to a Swift target at a later date.