cyan yelloW MaGenTa Black panTone 123 c Books for professionals By professionals® The eXperT’s Voice® in open source companion NNooww ccoovveerrss eBook Available Beginning Ruby: From Novice to Professional, RRuubbyy 11..99!! SecoNd editioN Beginning Beginning Dear Reader, R Beginning Ruby is the only book you’ll need to go from not knowing Ruby at all to being proficient and confident enough to develop your own applications and learn more about the specific areas that interest you. With just this book, you’ll Ruby learn how to develop your own complete applications that can work online, u access databases, process files, and more. Thanks to the popularity of the Ruby on Rails web application framework, Ruby has rapidly become a major programming language in the last ten years, b roughly on a par with Python. Ruby is still growing and maturing, however, and now is an especially good time to learn it. I’ve written this book in a way that lets you quickly learn the language without being bamboozled with jargon, even if y you’ve only ever dabbled with programming before. I’ve also provided links to a multitude of online resources and documentation to help you progress further. My own Ruby learning experience is my motivation for writing this book. I wanted to write a book that didn’t assume you’re already a dynamic language or object-orientation expert. This book introduces the most basic of concepts, yet moves quickly enough that you won’t need to skip too much if you’re already familiar with certain areas. Most of the areas relevant to a professional Ruby developer are covered, too—even those not directly related to the language, From Novice to Professional such as database access and SQL. From the start, my ambition has been to write a book to educate and encour- age, rather than deliver dry facts. There are enough reference books out there, but very few that will show you how to program with Ruby in a guided, narrated way. This book not only shows you how to program with Ruby, it also teaches you how the Ruby community works, where to find help, and how to “walk the walk” and “talk the talk.” An instructional guide to the Ruby programming language. Peter Cooper Companion eBook SecoNd THE APRESS ROADMAP SeCoNd editioN editioN Practical Reporting with Ruby and Rails Beginning Ruby, Second Edition NetBeans™ Ruby See last page for details Scripting Intelligence and Rails IDE with JRuby on $10 eBook version Beginning Rails 3 Pulling Strings with Puppet SOURCE CODE ONLINE C Peter Cooper www.apress.com ISBN 978-1-4302-2363-4 o o 53999 p e Foreword by why the lucky stiff r US $39.99 Shelve in Ruby User level: 9 781430 223634 Beginner–Intermediate this print for content only—size & color not accurate spine = 1.2485" 656 page count Beginning Ruby From Novice to Professional S e econd dition Peter Cooper Beginning Ruby: From Novice to Professional, Second Edition Copyright © 2009 by Peter Cooper All rights reserved. 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For Laura and Penny Contents at a Glance Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxi About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxv About the Technical Reviewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxvii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxix Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxi PART 1 n n n Foundations and Scaffolding ChaPtER 1 Let’s Get It Started: Installing Ruby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 ChaPtER 2 Programming == Joy: A Whistle-Stop Tour of Ruby and Object Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 ChaPtER 3 Ruby’s Building Blocks: Data, Expressions, and Flow Control . . . . .31 ChaPtER 4 Developing Your First Ruby Application . . . . . . . . . . . . . . . . . . . . . . . . . . 77 ChaPtER 5 The Ruby Ecosystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 PART 2 n n n The Core of Ruby ChaPtER 6 Classes, Objects, and Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 ChaPtER 7 Projects and Libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161 ChaPtER 8 Documentation, Error Handling, Debugging, and Testing . . . . . . . .177 ChaPtER 9 Files and Databases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 ChaPtER 10 Deploying Ruby Applications and Libraries . . . . . . . . . . . . . . . . . . . . .247 ChaPtER 11 Advanced Ruby Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .275 ChaPtER 12 Tying It Together: Developing a Larger Ruby Application . . . . . . . .307 PART 3 n n n Ruby Online ChaPtER 13 Web Application Frameworks: Rails, Sinatra, and Ramaze . . . . . . . 349 ChaPtER 14 Ruby and the Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .413 iv ChaPtER 15 Networking, Sockets, and Daemons . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 ChaPtER 16 GUI-Based Desktop Application Development . . . . . . . . . . . . . . . . . . . 467 ChaPtER 17 Useful Ruby Libraries and Gems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .495 aPPENDIX a Ruby Primer and Review for Developers . . . . . . . . . . . . . . . . . . . . . . . . 547 aPPENDIX B Ruby Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575 aPPENDIX C Useful Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .589 INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .601 v Contents Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxi About the Author . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxv About the Technical Reviewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxvii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxix Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxi PART 1 n n n Foundations and Scaffolding ChaPtER 1 Let’s Get It Started: Installing Ruby . . . . . . . . . . . . . . . . . . . . . . . . .3 Installing Ruby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Apple Mac OS X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 Linux . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Other Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 ChaPtER 2 Programming == Joy: a Whistle-Stop tour of Ruby and Object Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Baby Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 irb: Interactive Ruby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Ruby Is English for Computers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Why Ruby Makes a Great Programming Language . . . . . . . . . . . . . .15 Trails for the Mind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 Turning Ideas into Ruby Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 How Ruby Understands Concepts with Objects and Classes . . . . . . 17 The Making of a Man . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Basic Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 From People to Pets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 vii viii nCONTENTS Everything Is an Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Kernel Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 Passing Data to Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 Using the Methods of the String Class . . . . . . . . . . . . . . . . . . . . . . . . . 26 Using Ruby Without Object Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 ChaPtER 3 Ruby’s Building Blocks: Data, Expressions, and Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Numbers and Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Basic Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Comparison Operators and Expressions . . . . . . . . . . . . . . . . . . . . . . .33 Looping Through Numbers with Blocks and Iterators . . . . . . . . . . . .35 Floating Point Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Text and Strings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 String Literals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 String Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 String Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Regular Expressions and String Manipulation . . . . . . . . . . . . . . . . . . . 44 Arrays and Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Basic Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 Splitting Strings into Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52 Array Iteration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Other Array Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Hashes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Basic Hash Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 Hashes Within Hashes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Flow Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59 if and unless . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60 ?, the Ternary Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 elsif and case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62 while and until . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 Code Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64 Other Useful Building Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Dates and Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 Large Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70