This site does a fantastic job of introducing you to the basics of Cocoa and Xcode. The tutorials are brilliantly laid out and easy to follow. I’ve completed the first two, and I have to say, that even though I know absolutely nothing about coding, I’m enjoying trying to learn it. I’m confused about a few things, but the tutorials are easy enough to follow, and I feel like I’ll be able to learn a lot from this site.
I’m sure there are more detailed and advanced books and such that are also fine resources, but this website is a fantastic starting point if you’re interested in learning how to code for the Mac.