Olsen - Eloquent Ruby

Reading Eloquent Ruby is like programming in Ruby itself: fun, surprisingly deep, and youll find yourself wishing it was always done this way. Wherever you are in your Ruby experience from novice to Rails developer, this book is a must read.

Ethan Roberts
Owner, Monkey Mind LLC

Eloquent Ruby lives up to its name. Its a smooth introduction to Ruby thats both well organized and enjoyable to read, as it covers all the essential topics in the right order. This is the book I wish Id learned Ruby from.

James Kebinger
Senior Software Engineer, PatientsLikeMe
www.monkeyatlarge.com

Rubys syntactic and logical aesthetics represent the pinnacle for elegance and beauty in the ALGOL family of programming languages. Eloquent Ruby is the perfect book to highlight this masterful language and Russs blend of wit and wisdom is certain to entertain and inform.

Michael Fogus
Contributor to the Clojure programming language and author of The Joy of Clojure

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Library of Congress Cataloging-in-Publication Data

Olsen, Russ.
Eloquent Ruby / Russ Olsen.
p. cm.
Includes index.
ISBN-13: 978-0-321-58410-6 (pbk. : alk. paper)
ISBN-10: 0-321-58410-4 (pbk. : alk. paper)
1. Ruby (Computer program language) I. Title.
QA76.73.R83O47 2011
005.133dc22
2010048388

Copyright 2011 Pearson Education, Inc.

All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to:

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Rights and Contracts Department
501 Boylston Street, Suite 900
Boston, MA 02116
Fax: (617) 671-3447

ISBN-13: 978-0-321-58410-6
ISBN-10: 0-321-58410-4

Text printed in the United States on recycled paper at RR Donnelley in Crawfordsville, Indiana.
Second printing, July 2011

To My Dad
Charles J. Olsen
Who never had a chance to write a book of his own,
which is a shame because it would have been
hilarious

Do you know why experienced Ruby programmers tend to reach for basic collections and hashes while programmers from other languages go for more specialized classes? Do you know the difference between strip, chop, and chomp, and why there are three such similar methods when apparently one might suffice? (Not to mention lstrip and rstrip!) Do you know the downsides of dynamic typing? Do you know why the differences between strings and symbols get so blurry, even to experienced Ruby developers? How about metaprogramming? What the heck is an eigenclass? How about protected methods? Do you know what theyre really about? Really? Are you sure?

Russ knows all that stuff and more. And if books are like babies, then Russ is that experienced mom who pops out her second child after a couple of hours of labor and is back at work a week later in her pre-pregnancy clothes as if nothing out of the ordinary happened. You know: the one all the other moms talk about in hushed tones of disbelief and reverence. Thats the way my series authors discuss Russ.

Not that theres anything small or insignificant about Russ bouncing new baby... eh, I mean book. On the contrary, weighing in at just over 400 pages, this tome is slightly larger than its older sibling Design Patterns in Ruby. The family resemblance is crystal clear: Russ is first and foremost your friend. His approachable writing style makes even the driest Ruby language topics engaging and funny. Like the way that symbols remind Russ of the eyes peering out from the tilted head of a confused but friendly dog.

Truth is, we need this kind of book now more than ever. Ruby has hit the mainstream with the force of a Hulk Smash, and the masses are paddling along well-known routes without full (heck, sometimes any) understanding of what makes their favorite frameworks and library APIs so vibrant and navigable. So for those not content with the basics, those who want to go beyond shallow understanding, this book goes deep. It helps readers achieve true mastery of Ruby, a programming language with some of the deepest, darkest pools of nuance and texture of all the major languages of modern times.

I know youre going to enjoy this book, just like I did. And if you do, please join me in encouraging Russ to get knocked up again soon.

Obie Fernandez, Professional Ruby Series Editor

Ive taught a fair number of Ruby classes over the years, but one particular class stands out in my mind. Class was over, and as I was going out the door one of my students, an experienced Java programmer, stopped me and voiced a complaint that I have heard many times since. He said that the hardest part of learning Ruby wasnt the syntax or the dynamic typing. Oh, he could write perfectly correct Ruby, sans semicolons and variable declarations. The problem was that something was missing. He constantly found himself falling back into his same old Java habits. Somehow his Ruby code always ended up looking much like what he would have written in Java. My answer to him was not to worry, you havent missed anythingyou just arent done learning Ruby.

What does it mean to learn a new programming language? Clearly, like my frustrated student, you need to understand the basic rules of the grammar. To learn Ruby you need to be aware that a new line usually starts a new statement, that a class definition starts with the word class, and that variable names start with a lowercase letterunless they start with an @. But you cant really stop there. Again, like my erstwhile student you will also need to know what all of that code does. Youll need to know that those statements are really expressions (since they all return a value) and that all of those classes starting with the class keyword can change over time. And youll need to know why those @variables are different from the plain vanilla variables.

But the punch line is that even after you master all of this, you are still not quite there. It turns out that computer languages share something fundamental with our everyday order-a-pizza human tongues: Both kinds of languages are embedded in a culture, a way of thinking about the world, an approach to solving problems. A formal understanding of the mechanics of Ruby isnt the same as really looking at the programming world through Ruby-colored glasses. You need to absorb the cultural part of Ruby, to see how real Rubyists use the language to solve problems.