www.it-ebooks.info Beta Book Agile publishing for agile developers Under Construction The book you’re reading is still under development. As part of our Beta book pr ogram, we’re releasing this copy well before a normal book would be released. That way you’re able to get this content a couple of months before it’s available in finished form, and we’ll get feedback to make the book even better. The idea is that everyone wins! Be warned. The book has not had a full technical edit, so it will contain errors. It has not been copyedited, so it will be full of typos and other weird- ness. And there’s been no effort spent doing layout, so you’ll find bad page breaks, over-long lines with little black rectangles, incorrect hyphenations, and all the other ugly things that you wouldn’t expect to see in a finished book. We can’t be held liable if you use this book to try to create a spiffy application and you somehow end up with a strangely shaped farm imple- ment instead. 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Where those designations appear in this book, and The Pragmatic Program- mers, LLC was aware of a trademark claim, the designations ha ve been printed in initial capital letters or in all capitals. The Pragmatic Starter Kit, The Pragmatic Programmer, Pragmatic Program- ming, Pragmatic Bookshelf and the linking g device are trademarks of The Pragmatic Pr ogra mmers, LLC. Every precaution was taken in the preparation of this book. However, the publisher assumes no responsibility for errors or omissions, or for damages that may result from the use of information (including program listings) contained herein. Our Pragmatic courses, workshops, and other products can help you and your team create better software and have more fun. For more information, as well as the latest Pragmatic titles, please visit us at http://www.pragprog.com. C opyright © 2010 The Pragmatic Programmers LLC. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior consent of the publisher. Printed in the United States of America. ISBN-10: 1-934356-54-9 ISBN-13: 978-1-934356-54-8 Printed on acid-free paper. B11.0 printing, November 24, 2010 Version: 2010-11-24 www.it-ebooks.info Contents Changes in the Beta Releases 10 Beta 11—November 24 . . . . . . . . . . . . . . . . . . . . . . . . . 10 Beta 10—October 28 . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Beta 9—October 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Beta 8—September 9 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Beta 7—August 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Beta 6—July 27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Beta 5—June 28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Beta 4—May 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Beta 3—May 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Beta 2—May 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Preface to the Fourth Edition 15 Acknowledgements 17 Introduction 19 Rails Simply Feels Right . . . . . . . . . . . . . . . . . . . . . . . . . 19 Rails Is Agile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Who This Book Is For . . . . . . . . . . . . . . . . . . . . . . . . . . 22 How To Read This Book . . . . . . . . . . . . . . . . . . . . . . . . . 22 Part I—Getting Started 26 1 Installing Rails 27 1.1 Installing on Windows . . . . . . . . . . . . . . . . . . . . . . 27 1.2 Installing on Mac OS X . . . . . . . . . . . . . . . . . . . . . 29 1.3 Installing on Linux . . . . . . . . . . . . . . . . . . . . . . . . 30 1.4 Choosing a Rails Version . . . . . . . . . . . . . . . . . . . . 31 1.5 Setting Up Your Development Environment . . . . . . . . . 32 1.6 Rails and Databases . . . . . . . . . . . . . . . . . . . . . . . 36 1.7 What We Just Did . . . . . . . . . . . . . . . . . . . . . . . . 37 www.it-ebooks.info CONTENTS 6 2 Instant Gratification 38 2.1 Creating a New Application . . . . . . . . . . . . . . . . . . . 38 2.2 Hello, Rails! . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 2.3 Linking Pages Together . . . . . . . . . . . . . . . . . . . . . 47 2.4 What We Just Did . . . . . . . . . . . . . . . . . . . . . . . . 49 3 The Architecture of Rails Applications 51 3.1 Models, Views, and Controllers . . . . . . . . . . . . . . . . 51 3.2 Rails Model Support . . . . . . . . . . . . . . . . . . . . . . . 54 3.3 Action Pack: The View and Controller . . . . . . . . . . . . 56 4 Introduction to Ruby 58 4.1 Ruby Is an Object-Oriented Language . . . . . . . . . . . . 58 4.2 Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.3 Logic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.4 Organizing Structures . . . . . . . . . . . . . . . . . . . . . . 66 4.5 Marshaling Objects . . . . . . . . . . . . . . . . . . . . . . . 69 4.6 Pulling It All Together . . . . . . . . . . . . . . . . . . . . . . 69 4.7 Ruby Idioms . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Part II—Building an Application 73 5 The Depot Application 74 5.1 Incremental Development . . . . . . . . . . . . . . . . . . . . 74 5.2 What Depot Does . . . . . . . . . . . . . . . . . . . . . . . . . 75 5.3 Let’s Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6 Task A: Creating the Application 81 6.1 Iteration A1: Creating the Products Maintenance Applica- t ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.2 Iteration A2: Making Prettier Listings . . . . . . . . . . . . . 88 7 Task B: Validation and Unit Testing 95 7.1 Iteration B1: Validating! . . . . . . . . . . . . . . . . . . . . . 95 7.2 Iteration B2: Unit Testing of Models . . . . . . . . . . . . . 100 8 Task C: Catalog Display 109 8.1 Iteration C1: Cr eating the Catalog Listing . . . . . . . . . . 109 8.2 Iteration C2: Adding a Page Layout . . . . . . . . . . . . . . 112 8.3 Iteration C3: Using a Helper to Format the Price . . . . . . 116 8.4 Iteration C4: Functional Testing of Controllers . . . . . . . 116 Report erratum this copy is (B11.0 printing, November 24, 2010) www.it-ebooks.info CONTENTS 7 9 Task D: Cart Creation 121 9.1 Iteration D1: Finding a Cart . . . . . . . . . . . . . . . . . . 121 9.2 Iteration D2: Connecting Products to Carts . . . . . . . . . 122 9.3 Iteration D3: Adding a Button . . . . . . . . . . . . . . . . . 124 10 Task E: A Smarter Cart 130 10.1 Iteration E1: Creating a Smarter Cart . . . . . . . . . . . . 130 10.2 Iteration E2: Handling Errors . . . . . . . . . . . . . . . . . 134 10.3 Iteration E3: Finishing the Cart . . . . . . . . . . . . . . . . 138 11 Task F: Add a Dash of Ajax 143 11.1 Iteration F1: Moving the Cart . . . . . . . . . . . . . . . . . 144 11.2 Iteration F2: Creating an Ajax-Based Cart . . . . . . . . . . 149 11.3 Iteration F3: Highlighting Changes . . . . . . . . . . . . . . 152 11.4 Iteration F4: Hiding an Empty Cart . . . . . . . . . . . . . . 154 11.5 Testing Ajax changes . . . . . . . . . . . . . . . . . . . . . . 158 12 Task G: Check Out! 163 12.1 Iteration G1: Capturing an Order . . . . . . . . . . . . . . . 163 12.2 Iteration G2: Atom Feeds . . . . . . . . . . . . . . . . . . . . 177 12.3 Iteration G3: Pagination . . . . . . . . . . . . . . . . . . . . . 181 13 Task H: Sending Mail 186 13.1 Iteration H1: Sending Confirmation E-mails . . . . . . . . . 186 13.2 Iteration H2: Integration Testing of Applications . . . . . . 193 14 Task I: Logging In 199 14.1 Iteration I1: Adding Users . . . . . . . . . . . . . . . . . . . 199 14.2 Iteration I2: Authenticating Users . . . . . . . . . . . . . . . 208 14.3 Iteration I3: Limiting Access . . . . . . . . . . . . . . . . . . 213 14.4 Iteration I4: Adding a Sidebar, More Administration . . . . 216 15 Task J: Internationalization 221 15.1 Iteration J1: Selecting the locale . . . . . . . . . . . . . . . . 222 15.2 Iteration J2: Translating the Store Front . . . . . . . . . . . 224 15.3 Iteration J3: Translating Checkout . . . . . . . . . . . . . . 231 15.4 Iteration J4: Add a Locale Switcher . . . . . . . . . . . . . . 237 16 Task K: Deployment and Production 241 16.1 Iteration K1: Deploying with Phusion Passenger and MySQL 243 16.2 Iteration K2: Deploying Remotely with Capistrano . . . . . 248 16.3 Iteration K3: Checking Up on a Deployed Application . . . 254 Report erratum this copy is (B11.0 printing, November 24, 2010) www.it-ebooks.info CONTENTS 8 17 Depot Retrospective 258 17.1 Rails Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . 258 17.2 Documenting What We Have Done . . . . . . . . . . . . . . 261 Part III—Rails In Depth 263 18 Finding Your Way Around Rails 264 18.1 Where things go . . . . . . . . . . . . . . . . . . . . . . . . . 264 18.2 Naming Conventions . . . . . . . . . . . . . . . . . . . . . . 273 19 Active Record 277 19.1 Defining your Data . . . . . . . . . . . . . . . . . . . . . . . . 277 19.2 Locating and Traversing Records . . . . . . . . . . . . . . . 282 19.3 Creating, Reading, Updating, and Deleting (CRUD) . . . . 285 19.4 Participating in the Monitoring Process . . . . . . . . . . . 301 19.5 Transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 20 Action Dispatch and Action Controller 313 20.1 Dispatching Requests to Controllers . . . . . . . . . . . . . 313 20.2 Processing of Requests . . . . . . . . . . . . . . . . . . . . . 324 20.3 Objects and operations that span requests . . . . . . . . . 335 21 Action View 345 21.1 Using Templates . . . . . . . . . . . . . . . . . . . . . . . . . 345 21.2 Generating Forms . . . . . . . . . . . . . . . . . . . . . . . . 347 21.3 Processing Forms . . . . . . . . . . . . . . . . . . . . . . . . 350 21.4 Uploading Files to Rails Applications . . . . . . . . . . . . . 352 21.5 Using Helpers . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 21.6 Reducing Maintenance with Layouts and Partials . . . . . 362 22 Caching 371 22.1 Page Caching . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 22.2 Expiring Pages . . . . . . . . . . . . . . . . . . . . . . . . . . 374 22.3 Fragment Caching . . . . . . . . . . . . . . . . . . . . . . . . 380 23 Migrations 386 23.1 Creating and Running Migrations . . . . . . . . . . . . . . . 386 23.2 Anatomy of a Migration . . . . . . . . . . . . . . . . . . . . . 389 23.3 Managing Tables . . . . . . . . . . . . . . . . . . . . . . . . . 393 23.4 Advanced Migrations . . . . . . . . . . . . . . . . . . . . . . 397 23.5 When Migrations Go Bad . . . . . . . . . . . . . . . . . . . . 401 23.6 Schema Manipulation Outside Migrations . . . . . . . . . . 402 Report erratum this copy is (B11.0 printing, November 24, 2010) www.it-ebooks.info CONTENTS 9 24 Non-Browser Applications 404 24.1 A Standalone Application Using Active Record . . . . . . . 404 24.2 A Library Function Using Active Support . . . . . . . . . . 405 24.3 A Remote Application Using Active Resource . . . . . . . . 410 25 Rails’ Dependencies 416 25.1 Generating XML with Builder . . . . . . . . . . . . . . . . . 416 25.2 Generating HTML with ERb . . . . . . . . . . . . . . . . . . 418 25.3 Managing Dependencies with Bundler . . . . . . . . . . . . 420 25.4 Interfacing with the web server with Rack . . . . . . . . . . 422 25.5 Automating Tasks with Rake . . . . . . . . . . . . . . . . . . 426 25.6 Survey of Rails’ Dependencies . . . . . . . . . . . . . . . . . 427 26 Rails Plugins 431 26.1 Credit Card Processing with Active Merchant . . . . . . . . 431 26.2 Saving Bandwidth with Asset Packager . . . . . . . . . . . 433 26.3 Beautifying our Markup with Haml . . . . . . . . . . . . . . 435 26.4 Write Less and Do More with JQuery . . . . . . . . . . . . . 438 26.5 Finding more at RailsPlugins.org . . . . . . . . . . . . . . . 440 27 Where to Go From Here 443 A Bibliography 445 Index 446 Report erratum this copy is (B11.0 printing, November 24, 2010) www.it-ebooks.info Changes in the Beta Releases Beta 11—November 24 This beta incorporates a substantial amount of feedback from a number of sources including errata, formal reviews, and from the wonderful editor of this book. For the first time since putting this book out in beta, I am going to suggest that if you are well under way with Depot using a previous beta, consider keeping on with that beta. While there has been no major changes, there have been enough minor changes that those that wish to use this book are encouraged to start over. This draft has also been tested against the Rails 3.0.3 r elease. No changes were needed to make the code in this book work against that release. As always, thanks for all of the wonderful feedback via the errata, forums, and other venues. At this time I would like to specifically thank Johnathan Ritzi, David Kapp, and Jason Holloway. If you spot something, it is not too late to make a comment: there will be at least one more errata sweep before final printing. Beta 10—October 28 This beta introduces a chapter on plugins and completes the first draft. Plug- ins are not merely an afterthought or an advanced feature of Rails, with Rails 3.0 it is a fully architected way to augment or even replace base Rails func- tionality. This also completes the first draft. If you spot something missing, now would be an excellent time to report it via the forums or via an errata. After a few weeks of addressing comments it will be onto production where formatting and typographical and indexing glitches will be resolved. This draft has also been tested against the Rails 3.0.1 r elease. No changes were needed to make the code in this book work against that release. www.it-ebooks.info [...]... Acknowledgements You’d think that producing a new edition of a book would be easy After all, you already have all the text It’s just a tweak to some code here and a minor wording change there, and you’re done You’d think It’s difficult to tell exactly, but our impression is that creating each edition of Agile Web Development with Rails took about as much effort as the first edition Rails is constantly evolving and,... starting with half of a really good application already in place But there’s something else to Rails—something that’s hard to describe Somehow, it just feels right Of course, you’ll have to take our word for that until you write some Rails applications for yourself (which should be in the next 45 minutes or so ) That’s what this book is all about Rails Is Agile The title of this book is Agile Web Development. .. any suggestions and answers that you may have to questions others may have posted Let’s get started! The first steps are to install Ruby and Rails and to verify the installation with a simple demonstration Agile Web Development with Rails I found it in our local bookstore, and it seemed great!” —Dave’s mum 3 http://forums.pragprog.com/forums/148 4 http://www.pragprog.com/titles/rails4/errata 5 http://www.pragprog.com/wikis/wiki/RailsPlayTime... implementation of a wide range of so-called Web 2.0 applications Why is that? Rails Simply Feels Right First, a large number of developers were frustrated with the technologies they were using to create web applications It didn’t seem to matter whether they were using Java, PHP, or NET—there was a growing sense that their job was just too damn hard And then, suddenly, along came Rails, and Rails was easier But... and my preferences tend toward Vim and Ubuntu, we both share a love for the command line and getting our fingers dirty with code—starting with tangible examples before diving into heavy theory Since the time the third edition was published (and, in fact, since the first, second and third editions), much has changed Rails is in the process of being significantly refactored, mostly internally A number of... along with support for test fixtures and stubs during testing, gives developers the safety net they need when making those changes With a good set of tests in place, changes are less nerve-racking Rather than constantly trying to tie Rails processes to the agile principles, we’ve decided to let the framework speak for itself As you read through the tutorial chapters, try to imagine yourself developing web. .. partially updated to reflect the new direction, but will continue to work with Beta 3 Report erratum this copy is (B11.0 printing, November 24, 2010) 14 www.it-ebooks.info Preface to the Fourth Edition When Dave asked me to join as a coauthor of the third edition of this book, I was thrilled After all, it was from the first printing of the first edition of this book that I had learned Rails Dave and I also have... Doug Rhoten, Gary Sherman, Davanum Srinivas, Stefan Turalski, and José Valim Additionally, each edition of this book has been released as a beta book: early versions were posted as PDFs, and people made comments online And comment they did: more than 800 suggestions and bug reports were posted for this edition alone The vast majority ended up being incorporated, making this book immeasurably more useful... all about Rails Is Agile The title of this book is Agile Web Development with Rails You may be surprised to discover that we don’t have explicit sections on applying agile practices X, Y, and Z to Rails coding The reason is both simple and subtle Agility is part of the fabric of Rails Let’s look at the values expressed in the Agile Manifesto as a set of four preferences:1 • Individuals and interactions... Rails development process isn’t driven by documents You won’t find 500-page specifications at the heart of a Rails project Instead, you’ll find a group of users and developers jointly exploring their need and the possible ways of answering that need You’ll find solutions that change as both the developers and the users become more experienced with the problems they’re trying to solve You’ll find 1 http://agilemanifesto.org/ . & Dave www.it-ebooks.info Agile Web Development with Rails Fourth Edition Sam Ruby Dave Thomas David Heinemeier Hansson with Leon Breedt Mike Clark James. our impression is that creating each edition of Agile Web Development with Rails took about as much effort as the first edition. Rails is constantly evolving