Richard Warren 
Objective-C Boot Camp [EPUB ebook] 
Foundation and Patterns for iOS Development

This ebook offers basic training for the Objective-C programming language and explores the vital parts of the elegant language. This guide will give you enough information to get started, while pointing out many key features and common mistakes. While previous knowledge with objective-oriented programming is not necessary, the guide assumes you have a basic understanding of other C-like programming languages (C, C++, or Java, for example).