If you’re already a programmer, this book an excellent way to learn Ruby. It shows how to apply a variety of common and largely language-independent programming structures (“design patterns”) in “the Ruby way”. Along the way, you get a great introduction to what makes Ruby unique, and the idioms commonly used in the Ruby community. I especially liked that the author often showed multiple implementations of each pattern, each implementation being more elegant and Ruby-esque than the last, and included a discussion of when each might (and might not!) be appropriate. I also appreciated the helpful discussion of the ways you might shoot yourself in the foot with each pattern in Ruby, as well as the pointers to where you could find the pattern used in Ruby “in the wild” (in various software freely available on the Internet).

Design Patterns in Ruby is written with the idea that while the reader might be a good programmer, they may have somehow missed what Design Patterns are, or the reader might not know much about Ruby. The first two chapters rectify this by introducing the reader to what exactly these Design Patterns are. The author explains precisely which of the 14 of the original 23 “Gang of Four” patterns are covered in the book, and reasons why the 14 patterns were chosen. Chapter 2 is a quick introduction to Ruby, just to ensure everyone is on the same page. The author, in a single chapter, clearly explained concepts that other books I have read couldn’t clearly convey, even after several chapters. Any doubts that I had of the author’s abilities in explaining Design Patterns in a way that I would understand were completely gone by these chapters.

The actual Design Patterns in Design Patterns in Ruby have a similar format throughout the rest of the book. First, a small anecdote begins the chapter, explaining either a real-life situation where the patterns would be handy, or tying the pattern to one of the other patterns in the book. The meat of the chapter describes how one would implement the pattern, usually starting with a direct port from another language like C++ or Java, and gradually working it into something more Ruby-like by the end of the section. After the pattern is worked into a more Ruby-like format, the author then describes how to really abuse the pattern. Lastly, the author points out where this pattern is used in the Ruby, Rails, or other Ruby code, followed by a quick summary. This format works quite well, especially for programmers just starting in both Ruby and Design Patterns, while advanced programmers will learn better and more effective ways for implementing (or abusing) the patterns. Providing where the pattern is used in the code is also an excellent learning tool for the reader, and gives a baseline for the reader on where to look for more examples. The format also makes the book engaging. I found myself wanting to read the book, which is an experience I can’t say I shared with the original Gang of Four Design Patterns book.

In addition to 14 of the Gang of Four patterns, the author talks about three Ruby-specific patterns. The first is the Domain Specific Language (DSL) pattern. Rather than defaulting to discussing Active Record (arguably the most famous DSL in Ruby), the author actually creates a DSL called “PackRat” which is a language for managing backups. The second pattern is Metaprogramming, which is ubiquitous in Ruby. The last pattern in the book is Configuration Over Configuration, the mantra of Rails. Each of these patterns compliments the other patterns in the book, and add to the original patterns discussed earlier in the book.
Design Patterns in Ruby is an exceptional book. It distills the best of the “Gang of Four” patterns that are of significance to Ruby Programmers, while adding several patterns that show up throughout Ruby and Ruby on Rails code. The author’s style and the book’s format make for an easy and informative reading experience. I can heartily recommend this book for all Ruby developers, both beginners and experts, and can especially recommend this book for those like myself who didn’t think the original Design Patterns was anything to give attention. Design Patterns in Ruby has earned a permanent place on my shelf.

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written by bsigwa