[masklinn]

Cocoa and Cocoa Touch are integral to being paid for Obj-C, and they're by far the hardest part of it.

Learning objective-c, especially if you already know C, is pretty easy. The syntax is a bit weird but not hard, then you've got a few quirks and stuff, but fundamentally you can build a working model of the language in half a day tops if you're already a developer.

Understanding Apple's conventions (libraries, memory management, etc...) and merely knowing where to find the stuff you need in the doc, that's what take time. Cocoa is huge and is a complex beast, even if you don't dive into the C "Core*" stuff and remain at the NS/UI levels.