Write powerful Ruby code that is easy to maintain and change. With metaprogramming, you can produce elegant, clean, and beautiful programs. Once the domain of expert Rubyists, metaprogramming is now accessible to programmers of all levels. This thoroughly revised and updated second edition of the bestselling Metaprogramming Ruby explains metaprogramming in a down-to-earth style and arms you with a practical toolbox that will help you write your best Ruby code ever.

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About this Book

  • 250 pages
  • Published:
  • Release: P1.0 (2014-08-12)
  • ISBN: 978-1-94122-212-6

Dig under the surface and explore Ruby’s most advanced feature: a collection of techniques and tricks known as metaprogramming. In this book, you’ll learn metaprogramming as an essential component of Ruby and discover the deep, non-obvious details of the language. Once you understand the tenets of Ruby, including the object model, scopes, and singleton classes, you’re on your way to applying metaprogramming both in your daily work assignments and in your fun, after-hours projects.

Metaprogramming Ruby, Second Edition makes mastering the language enjoyable. The book is packed with:

  • Pragmatic examples of metaprogramming in action, many of which come straight from real-life gems such as Rails.
  • Programming challenges that let you experiment and play with some of the most out-there metaprogramming concepts.
  • Metaprogramming “spells”—33 practical recipes and idioms that you can study and apply right now, to write code that is sure to impress.

This completely revised new edition covers the new features in Ruby 2.0 and 2.1, and contains code from the latest Ruby libraries, including Rails 4. Most examples are new, “from the wild,” with more recent libraries. And the book reflects current ideas of when and how much metaprogramming you should use.

Whether you’re a Ruby apprentice on the path to mastering the language or a Ruby wiz in search of new tips, this book is for you.

What You Need

Ruby 2.x, Ruby 1.9, or a recent version of JRuby.

User Level

Contents and Extracts

Introduction
  • Metaprogramming Ruby
    • The M Word
      • Ghost Towns and Marketplaces
      • The Story of Bob, Metaprogrammer
      • Metaprogramming and Ruby
    • Monday: The Object Model
      • Open Classes
      • Inside the Object Model
      • Quiz: Missing Lines
      • What Happens When You Call a Method?
      • Quiz: Tangle of Modules
      • Wrap-Up
    • Tuesday: Methods excerpt
      • A Duplication Problem
      • Dynamic Methods
      • method_missing
      • Quiz: Bug Hunt
      • Blank Slates
      • Wrap-Up
    • Wednesday: Blocks
      • The Day of the Blocks
      • Quiz: Ruby#
      • Blocks Are Closures excerpt
      • instance_eval()
      • Callable Objects
      • Writing a Domain-Specific Language
      • Quiz: A Better DSL
      • Wrap-Up
    • Thursday: Class Definitions
      • Class Definitions Demystified
      • Quiz: Class Taboo
      • Singleton Methods
      • Singleton Classes
      • Quiz: Module Trouble
      • Method Wrappers
      • Quiz: Broken Math
      • Wrap-Up
    • Friday: Code That Writes Code
      • Coding Your Way to the Weekend
      • Kernel#eval
      • Quiz: Checked Attributes (Step 1)
      • Quiz: Checked Attributes (Step 2)
      • Quiz: Checked Attributes (Step 3)
      • Quiz: Checked Attributes (Step 4)
      • Hook Methods
      • Quiz: Checked Attributes (Step 5)
      • Wrap-Up
    • Epilogue
  • Metaprogramming in Rails
    • Preparing for a Rails Tour
      • Ruby on Rails
      • Installing Rails
      • The Rails Source Code
    • The Design of ActiveRecord
      • A Short ActiveRecord Example
      • How ActiveRecord Is Put Together
      • A Lesson Learned
    • ActiveSupport’s Concern Module excerpt
      • Rails Before Concern
      • ActiveSupport::Concern
      • A Lesson Learned
    • The Rise and Fall of alias_method_chain
      • The Rise of alias_method_chain
      • The Fall of alias_method_chain
      • A Lesson Learned
    • The Evolution of Attribute Methods
      • Attribute Methods in Action
      • A History of Complexity
      • A Lesson Learned
    • One Final Lesson
      • Metaprogramming Is Just Programming
  • Appendixes
    • Common Idioms
      • Mimic Methods
      • Nil Guards
      • Self Yield
      • Symbol#to_proc()
    • Domain-Specific Languages
      • The Case for Domain-Specific Languages
      • Internal and External DSLs
      • DSLs and Metaprogramming
    • Spell Book
      • The Spells

About the Author

Paolo Perrotta has fifteen years of experience as a developer, ranging from embedded to enterprise software, computer games, and web applications. Paolo lives a nomadic life, mentoring agile teams throughout Europe. He has a base camp in Bologna, Italy. He loves Ruby.

Comments and Reviews

  • This is the one book about Ruby that makes you go “So that’s how it works” over and over again, as concepts such as the object model, DSLs, and blocks fall into place with that satisfying “Click!” sound. It’s a great guide to what happens under the hood of a language that seems to involve a kind of magic deep inside. I highly recommend it.

    —Peter Bakhirev Lead software engineer Gilt City
  • The previous edition of Metaprogramming Ruby changed my life and my code, and helped me get my first programming job. You would think there would be no way to improve on a book that good, but Paolo Perrotta has done it. Learn to unlock the hidden potential of this beautiful language, and fall in love with Ruby again.

    —Richard Schneeman Programmer Heroku
  • For gem authors and application developers alike, this book lays down the foundation everyone needs to harness the full power of Ruby. Paolo describes metaprogramming in a fun and approachable way for all skill levels. The knowledge garnered from reading this book will help you write cleaner code and work more effectively with legacy codebases.

    —Paul Elliott Rocketeer Hashrocket
  • If you want to follow the path of Ruby metaprogramming mastery, then this book is the best companion you can think of, no matter what your level is. I had struggled with Ruby metaprogramming for years until I read this book; now it all makes sense.

    —Fabien Catteau Software developer Tech-Angels
  • This is a book that everyone who wants to have a deeper understanding of the inner workings of Ruby and Ruby on Rails should read. The “spells” described in this book are invaluable tools to understand and use Ruby to its full extent. This is not only about metaprogramming, but also about taking your Ruby programming to a different level.

    —Kosmas Chatzimichalis Software engineer
  • I’m a huge Python fan, so I was supposed to disregard Ruby. Paolo made me appreciate it. Not only is Metaprogramming Ruby the book that allowed me to wrap my head around this esoteric and fascinating topic, but it also made me rethink the way I write code in other languages.

    —Arialdo Martini Programmer JobRapido.com
  • This book uncovers all the ins and outs of the art of metaprogramming in Ruby, with a no-nonsense approach and an irony that transpires from vibrant prose, never boring, without compromising any of its insightfulness. Metaprogramming Ruby is one of those books that any serious Rubyist (and even the pros) will want to revisit from time to time.

    —Piergiuliano Bossi Principal engineer lead Points
  • Metaprogramming Ruby has been a hugely influential book for me, especially during a time when I wanted to learn about the inner workings of Ruby. Paolo “Nusco” Perrotta made what is normally a complex topic fun, enjoyable, and very approachable.

    —Josh Kalderimis CEO Travis CI