Product Description

Praise for Design Patterns in Ruby

"Design Patterns in Ruby documents smart ways to resolve many problems that Ruby developers commonly encounter. Russ Olsen has done a great job of selecting classic patterns and augmenting these with newer patterns that have special relevance for Ruby. He clearly explains each idea, making a wealth of experience available to Ruby developers for their own daily work."

—Steve Metsker, Managing Consultant with Dominion Digital, Inc.

"This book provides a great demonstration of the key 'Gang of Four' design patterns without resorting to overly technical explanations. Written in a precise, yet almost informal style, this book covers enough ground that even those without prior exposure to design patterns will soon feel confident applying them using Ruby. Olsen has done a great job to make a book about a classically 'dry' subject into such an engaging and even occasionally humorous read."

—Peter Cooper

"This book renewed my interest in understanding patterns after a decade of good intentions. Russ picked the most useful patterns for Ruby and introduced them in a straightforward and logical manner, going beyond the GoF's patterns. This book has improved my use of Ruby, and encouraged me to blow off the dust covering the GoF book."

—Mike Stok

"Design Patterns in Ruby is a great way for programmers from statically typed objectoriented languages to learn how design patterns appear in a more dynamic, flexible language like Ruby."

—Rob Sanheim, Ruby Ninja, Relevance

Most design pattern books are based on C++ and Java. But Ruby is different—and the language's unique qualities make design patterns easier to implement and use. In this book, Russ Olsen demonstrates how to combine Ruby's power and elegance with patterns, and write more sophisticated, effective software with far fewer lines of code.

After reviewing the history, concepts, and goals of design patterns, Olsen offers a quick tour of the Ruby language—enough to allow any experienced software developer to immediately utilize patterns with Ruby. The book especially calls attention to Ruby features that simplify the use of patterns, including dynamic typing, code closures, and "mixins" for easier code reuse.

Fourteen of the classic "Gang of Four" patterns are considered from the Ruby point of view, explaining what problems each pattern solves, discussing whether traditional implementations make sense in the Ruby environment, and introducing Ruby-specific improvements. You'll discover opportunities to implement patterns in just one or two lines of code, instead of the endlessly repeated boilerplate that conventional languages often require.

Design Patterns in Ruby also identifies innovative new patterns that have emerged from the Ruby community. These include ways to create custom objects with metaprogramming, as well as the ambitious Rails-based "Convention Over Configuration" pattern, designed to help integrate entire applications and frameworks.

Engaging, practical, and accessible, Design Patterns in Ruby will help you build better software while making your Ruby programming experience more rewarding.

Product Details

• Amazon Sales Rank: #49858 in Books
• Published on: 2007-12-20
• Original language: English
• Number of items: 1
• Binding: Hardcover
• 384 pages

About the Author

Russ Olsen has been building software for more than twenty-five years. He has led projects through several generations of programming technologies, from FORTRAN to C to C++ to Java, and now Ruby. He has been using and teaching Ruby since 2002. Olsen writes the popular technology blog Technology As If People Mattered (http://www.russolsen.com).

Excerpt. © Reprinted by permission. All rights reserved.

A former colleague of mine used to say that thick books about design patterns were evidence of an inadequate programming language. What he meant was that, since design patterns are the common idioms of code, a good programming language should make them very easy to implement. An ideal language would so thoroughly integrate the patterns that they would almost disappear from sight.

To take an extreme example, in the late 80's I worked on a project that produced object oriented code in C. Yes, C, not C++. We pulled this off by having each "object" (actually a C structure) point off to a table of function pointers. We operated on our "objects" by chasing the pointer to the table and calling functions out of the table, thereby simulating a method call on an object. It was awkward and messy, but it worked. Had we thought of it, we might have called this technique the "object oriented" pattern. Of course with the advent of C++ and then Java, our object oriented pattern disappeared, absorbed so thoroughly into the language that it vanished from sight. Today, we don't usually think of object orientation as a pattern—it is too easy.

But many things are still not easy enough. The justly famous Gang of Four book, (Design Patterns: Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson, and Vlissides) is required reading for every software engineer today. But actually implementing many of the patterns described in Design Patterns with the languages in widespread use today, Java and C++ and perhaps C#, looks and feels a lot like my 1980s vintage handcrafted object system. Too painful. Too verbose. Too prone to bugs.

The Ruby programming language takes us a step closer to my old friend's ideal, a language that makes implementing patterns easy, so easy that sometimes they fade into the background. Building patterns in Ruby is easier for a number of reasons:

• Ruby is dynamically typed. By dispensing with static typing, Ruby dramatically reduces the code overhead of building most programs, including those that implement patterns.

• Ruby has code closures. Ruby allows us to pass around chunks of code and associated scope without having to laboriously construct entire classes and objects that do nothing else.

• Ruby classes are real objects. Since a class in Ruby is just another object, we can do any of the usual runtime things to a Ruby class that we can do to any object. At runtime we can create totally new classes. We can also modify existing classes by adding or deleting methods. We can even clone a class and change the copy, leaving the original alone.

• Ruby has an elegant system of code reuse. In addition to garden variety inheritance, Ruby provides also allows us to define mixins, which are a simple but flexible way to write code that can be shared among several classes.

All of this makes code in Ruby compressible: In Ruby, like Java and C++, you can implement very sophisticated ideas, but with Ruby it is possible to hide the details of your implementations much more effectively. As you will see on the pages that follow, many of the design patterns that require many lines of endlessly repeated boiler plate code in traditional static languages require only one or two lines in Ruby. You can make a class into a singleton with a simple include Singleton. You can delegate as easily as you can inherit. Since Ruby enables you to say more interesting things in each line of code, you end up with less code.

This is not just a question of keyboard laziness, it is an application of the DRY (Don't Repeat Yourself) principal. I don't think anyone today would mourn the passing of my old object oriented pattern in C—it worked for me, but it made me work for it, too. In the same way, the traditional implementations of many design patterns work, but they make you work too. Ruby is a real step forward to be able to do that work only once and compress it out of the bulk of our code. In short, Ruby allows us to concentrate on the real problems that we are trying to solve instead of the plumbing. I hope that this book will help you see how.

Who Is This Book For?

Simply put, this book is for developers who want to know how to build significant software in Ruby. I assume that you are familiar with object oriented programming, but you don't really need any knowledge of design patterns —you can pick that up as you go through the book.

You also don't need a lot of Ruby knowledge to read this book profitably: you can find a quick introduction to the language in Chapter 2 and I do try to explain any Ruby specific language issues as we go.

How Is This Book Organized?

This book is divided into three parts. First there are a couple of introductory chapters, starting with the briefest outline of the history and background of the whole Design Patterns movement and ending with a quick tour of the Ruby language, at the "just enough to be dangerous" level.

The second section, which takes up the bulk of these pages, looks at a number of the original Gang of Four patterns from a Ruby point of view. What problem is this pattern trying to solve? What does the traditional implementation of the pattern, the implementation given by the Gang of Four look like in Ruby? Does the traditional implementation make sense in Ruby? Does Ruby provide us with any alternatives that will make solving the problem easier?

The final section of this book looks at a three patterns that have emerged from the Ruby.

A Word of Warning

I cannot sign my name to a book about design patterns without repeating the mantra that I have been muttering for many years now: design patterns are little spring loaded solutions to common programming problems. Ideally, when the appropriate kind of problem comes along, you should trigger the design pattern and the problem is solved. It is that first part, the bit about waiting for the appropriate problem to come along, that some engineers have trouble with. You cannot say that you are correctly applying a design pattern unless you are confronting the problem that the pattern is supposed to solve.

The reckless use of every design pattern on the menu to solve nonexistent problems has given design patterns a bad name in some circles. I would contend that Ruby makes it easier to write an adapter that uses a factory method to get a proxy to the builder which creates the command which coordinates the operation of adding two plus two. Ruby will make that easier, but even in Ruby it will not make any sense.

Nor can you look at program construction as a simple process of piecing together some existing design patterns in new combinations. Any interesting program is going to have unique sections, bits of code that fit that specific problem perfectly and no other. Design patterns are meant to help you recognize and solve the common problems that arise over and over when you are building software. The advantage of design patterns is that they let you rapidly get past the problems that someone has already solved, so that you can get on to the hard stuff, the code that is unique to your situation. Design patterns are not the universal elixir, the magic potion that will fix all of your design problems. They are simply one technique, albeit a very useful technique, that you can use to build programs.

Customer Reviews

Excellent introduction to Ruby for existing programmers
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).

Advanced Ruby programming styles and idioms
This is a marvelous book, ideal if you're an experienced object-oriented programmer who wants to learn to use Ruby with the idioms particular to it, and not remain frozen in the techniques of traditional, statically typed object-oriented languages. Ruby is a dynamically typed language with many unique features, and this book was invaluable in my learning to use it as such. There are 16 design patterns covered, 3 of which are particular to the Ruby development environment. With each pattern is presented first the traditional approach using Ruby as a straightforward OO language, followed by the Ruby approach which takes advantage of the idioms and techniques particular to the Ruby language. With each pattern is introduced a new Ruby idiom, making the book a tutorial in advanced Ruby programming techniques.

Design Patterns make sense with this book in Ruby
I never really understood the need for Design Patterns. After reading several blogs, and listening to other programmers, I thought that Design Patterns might even somehow be harmful to my programming education. I felt that just by learning what they were, I'd somehow pollute my thinking to the point where I wouldn't be able to program without seeing a pattern in there somewhere. When I heard of the book Design Patterns in Ruby, I flinched. What good could possibly come from introducing Design Patterns into Ruby, I asked myself? Fortunately, my initial prejudices were unfounded. Design Patterns in Ruby is not some secret plot to turn all of the Ruby programmers into mindless drones; it is a very thorough introduction to Ruby, Design Patterns, and Object Oriented Programming concepts. Design Patterns in Ruby helped me to finally look critically at Design Patterns, and see them as something not to be feared, but as something that could be useful, even in my Ruby programming.

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.