The Rails way

903 Pages·2008·2.558 MB·English

by  Obie Fernandez

T R W
HE AILS AY
Obie Fernandez
Upper Saddle River, NJ • Boston • Indianapolis • San Francisco
New York • Toronto • Montreal • London • Munich • Paris • Madrid
Capetown • Sydney • Tokyo • Singapore • Mexico City
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where
those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been
printed with initial capital letters or in all capitals.
The author and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of
any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential dam-
ages in connection with or arising out of the use of the information or programs contained herein.
The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales, which
may include electronic versions and/or custom covers and content particular to your business, training goals, marketing
focus, and branding interests. For more information, please contact:
U.S. Corporate and Government Sales
[phone]
[email protected]
For sales outside the United States please contact:
International Sales
[email protected]
This Book Is Safari Enabled
The Safari® Enabled icon on the cover of your favorite technology book means the book is available
through Safari Bookshelf. When you buy this book, you get free access to the online edition for 45
days.
Safari Bookshelf is an electronic reference library that lets you easily search thousands of technical books, find code sam-
ples, download chapters, and access technical information whenever and wherever you need it.
To gain 45-day Safari Enabled access to this book:
• Go to http://www.awprofessional.com/safarienabled
• Complete the brief registration form
• Enter the coupon code 52GH-T7VF-4T1U-ATFQ-DMJH
If you have difficulty registering on Safari Bookshelf or accessing the online edition, please e-mail
[email protected].
Visit us on the Web: www.awprofessional.com
Library of Congress Cataloging-in-Publication Data:
Fernandez, Obie.
The Rails way / Obie Fernandez.
p. cm.
Includes index.
ISBN 0-321-44561-9 (pbk. : alk. paper)
1. Ruby on rails (Electronic resource) 2. Object-oriented programming (Computer science) 3. Ruby (Computer pro-
gram language) 4. Web site development . 5. Application softare--Development. I. Title.
QA76.64F47 2007
005.1'17--dc22
2007039880
Copyright © 2008 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 permis-
sions, write to:
Pearson Education, Inc.
Rights and Contracts Department
75 Arlington Street, Suite 300
Boston, MA 02116
Fax: [phone]
This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0
or later (the latest version is presently available at http://www.opencontent.org/openpub/).
ISBN-13: 978-0-321-44561-9
ISBN-10: 0-321-44561-9
Text printed in the United States on recycled paper at R.R. Donnelly in Crawfordsville, IN.
First printing November 2007
Parts of this book contain material excerpted from the Ruby and Rails source code and API documentation, Copyright ©
2004-2006 by David Heinemeier Hansson under the MIT license. Chapter 18 contains material excerpted from the RSpec
source code and API documentation, Copyright © 2005-2007 The RSpec Development Team.
The MIT License reads:
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation
files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, mod-
ify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software
is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
Software.
THE SOFTWARE IS PROVIDED “AS IS,” WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PAR-
TICULAR PURPOSE, AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES, OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT, OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFT-
WARE OR THE USE OF OR OTHER DEALINGS IN THE SOFTWARE.
Associate Publisher Copy Editor
Mark Taub Margaret Berson
Acquisitions Editor Proofreader
Debra Williams Cauley Kathy Ruiz
Development Editor Technical Reviewer
Francis Hwang
Songlin Qiu
Sebastian Delmont
Managing Editor Wilson Bilkovich
Patrick Kanouse Courtenay Gasking
Senior Project Editor Sam Aaron
San Dee Phillips Nola Stowe
Susan Potter
Indexer
Jon Larkowski
Tim Wright
Publishing Coordinator
Cindy Teeters
Book Designer
Chuti Prasertsith
Composition
Mark Shirar
To Desi, my love, my companion, my muse.
xii Contents
Contents
Chapter 1 Rails Environments and Configuration 1
Startup 2
Default Environment Settings 2
Mode Override 2
Rails Gem Version 2
Bootstrapping 3
RubyGems 5
Initializer 6
Default Load Paths 6
Rails, Modules, and Auto-Loading Code 7
Builtin Rails Info 8
Configuration 9
Skipping Frameworks 9
Additional Load Paths 10
Log-Level Override 10
ActiveRecord Session Store 10
Schema Dumper 11
Observers 11
Time Zones 11
Additional Configuration 13
Development Mode 14
Automatic Class Reloading 15
The Rails Class Loader 15
Test Mode 17
Production Mode 17
Logging 18
Rails Log Files 20
Contents xiii
Log File Analysis 22
Syslog 24
Conclusion 25
References 25
Chapter 2 Working with Controllers 27
The Dispatcher: Where It All Begins 28
Request Handling 28
Getting Intimate with the Dispatcher 29
Render unto View… 31
When in Doubt, Render 32
Explicit Rendering 33
Rendering Another Action’s Template 33
Rendering a Different Template Altogether 34
Rendering a Partial Template 35
Rendering Inline Template Code 35
Rendering Text 35
Rendering Other Types of Structured Data 36
:json 36
:xml 36
Rendering Nothing 36
Rendering Options 37
:content_type 37
:layout 37
:status 37
Redirecting 39
Controller/View Communication 42
Filters 43
Filter Inheritance 44
Filter Types 46
Filter Classes 46
Inline Filter Method 47
Filter Chain Ordering 47
Around Filters 48
Filter Chain Skipping 49
xiv Contents
Filter Conditions 50
Filter Chain Halting 50
Streaming 51
send_data(data, options = {}) 51
Options for send_data 51
Usage Examples 52
send_file(path, options = {}) 52
Options for send_file 53
Usage Examples 55
Letting the Web Server Send Files 55
Conclusion 56
References 56
Chapter 3 Routing 57
The Two Purposes of Routing 58
Bound Parameters 60
Wildcard Components (“Receptors”) 61
Static Strings 62
The routes.rb File 63
The Default Route 65
Spotlight on the :id Field 66
Default Route Generation 67
Modifying the Default Route 68
The Ante-Default Route and respond_to 69
respond_to and the HTTP-Accept Header 70
The Empty Route 71
Writing Custom Routes 72
Using Static Strings 72
Using Your Own “Receptors” 73
A Note on Route Order 75
Using Regular Expressions in Routes 76
Default Parameters and the url_for Method 76
What Happened to :id? 77
Using Literal URLs 79
Route Globbing 79
Globbing Key-Value Pairs 80
Named Routes 81
Contents xv
Creating a Named Route 81
The Question of Using name_path Versus name_url 82
Considerations 83
What to Name Your Routes 83
Argument Sugar 84
A Little More Sugar with Your Sugar? 85
The Special Scope Method with_options 86
Conclusion 88
References 88
Chapter 4 REST, Resources, and Rails 89
REST in a Rather Small Nutshell 89
REST in Rails 91
Routing and CRUD 92
Resources and Representations 93
REST Resources and Rails 93
From Named Routes to REST Support 94
Reenter the HTTP Verb 96
The Standard RESTful Controller Actions 96
The PUT and DELETE Cheat 98
Singular and Plural RESTful Routes 98
The Special Pairs: new/create and edit/update 99
Singular Resource Routes 100
Nested Resources 101
Setting :path_prefix Explicitly 103
Setting :name_prefix Explicitly 103
Specifying RESTful Controllers Explicitly 105
All Together Now 105
Considerations 107
Deep Nesting? 108
RESTful Route Customizations 110
Extra Member Routes 110
Extra Collection Routes 111
Considerations 112
Controller-Only Resources 113
Different Representations of Resources 115
xvi Contents
The respond_to Method 116
Formatted Named Routes 117
The RESTful Rails Action Set 117
Index 118
Show 121
Destroy 121
New and Create 123
Edit and Update 124
Conclusion 125
Reference 126
Chapter 5 Reflecting on Rails Routing 127
Examining Routes in the Application Console 127
Dumping Routes 128
Anatomy of a Route Object 129
Recognition and Generation in the Console 132
Named Routes in the Console 134
Testing Routes 135
The Routing Navigator Plugin 136
Conclusion 137
References 137
Chapter 6 Working with ActiveRecord 139
The Basics 140
Migrations 142
Creating Migrations 143
Naming Migrations 144
Migration Pitfalls 145
Migration API 146
create_table(name, options) 147
Defining Columns 149
Column Type Mappings 150
Column Options 151
Decimal Precision 152
Column Type Gotchas 152
Custom Data Types 154
“Magic” Timestamp Columns 154
Macro-Style Methods 155
Relationship Declarations 155
Contents xvii
Convention over Configuration 156
Pluralization 157
Should I Report INFLECTOR Bugs to the Core Team? 158
Setting Names Manually 158
Legacy Naming Schemes 159
Defining Attributes 160
Default Attribute Values 160
Serialized Attributes 162
CRUD: Creating, Reading, Updating, Deleting 163
Creating New ActiveRecord Instances 163
Reading ActiveRecord Objects 164
find 164
Reading and Writing Attributes 166
Hash Notation 167
The attributes Method 168
Accessing and Manipulating Attributes Before They Are Typecast 168
Reloading 169
Dynamic Attribute-Based Finders 169
Custom SQL Queries 171
The Query Cache 172
Logging 173
Default Query Caching in Controllers 173
Limitations 174
Updating 174
Updating by Condition 176
Updating a Particular Instance 176
Updating Specific Attributes 177
Convenience Updaters 177
Controlling Access to Attributes 178
Deleting and Destroying 178
Database Locking 179
Optimistic Locking 180
Handling StaleObjectError 181
Pessimistic Locking 182
Considerations 183
Advanced Finding 183
Conditions 183
Boolean Conditions 185
Ordering of Find Results 186