I'm a hobbyist programmer with a little object oriented experience. I found this book to be exactly what I needed to give me a concise description of the various structures and source code conventions for writing programs in Objective-C, specifically in Xcode. Things like "How do I format an Objective-C header?" to "What was the syntax for setting up @interface statements?" were extremely helpful. The book goes into what ARC (Automatic Reference Counting) is and how to use it, as well as basics of using Autorelease and even manual memory management if you really need to go there. It is full of small example code which makes it immediately clear what Xcode expects you to use for most common programming structures, and does a very good job of laying out the basics of the MacOS and iOS core frameworks and services. I definitely recommend this book for programmers needing a reference or primer for transitioning to Objective-C.