Ruby Hacking Guide
by Minero Aoki
The RHG is a book that explains how the ruby interpreter (the official C implementation of the Ruby language) works internally. To fully understand it, you need a good knowledge of C and Ruby. This book is going to investigate ruby as a whole.
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by Zed A. Shaw - LCodeTHW
The book assumes absolutely no prior programming knowledge and will guide you carefully and slowly through the learning process. When you are done with it you will have the skill to move on to other books about Ruby and be ready to understand them.
by Matt Aimonetti - O'Reilly Media
MacRuby is Apple's implementation of the Ruby programming language which uses Objective-C runtime. This book is an introduction to MacRuby. Topics covered: Introduction, The Cocoa Environment, Foundation, Application Kit, Core Data, Xcode.
by Mitch Guthrie - bigfatrails.com
A book designed around teaching Ruby on Rails in a precept upon precept fashion. Both theory and practice driving your knowledge. If you are a beginner, the purpose of this book is to simply get you there in small, manageable steps.
by Avdi Grimm - objectsonrails.com
The book is documenting some guidelines and ideas for applying classic object-oriented thought to Ruby on Rails applications. It is aimed at the working Rails developer who is looking to grow and evolve Rails projects while keeping them flexible.