Contents
- Chapter 1 From zero to deploy
- Chapter 2 A demo app
- Chapter 3 Mostly static pages
- Chapter 4 Rails-flavored Ruby
- Chapter 5 Filling in the layout
- Chapter 6 Modeling users
- Chapter 7 Sign up
- Chapter 8 Sign in, sign out
- Chapter 9 Updating, showing, and deleting users
- Chapter 10 User microposts
- Chapter 11 Following users
My former company (CD Baby) was one of the first to loudly switch to Ruby on Rails, and then even more loudly switch back to PHP (Google me to read about the drama). This book by Michael Hartl came so highly recommended that I had to try it, and the Ruby on Rails Tutorial is what I used to switch back to Rails again.
Though I’ve worked my way through many Rails books, this is the one that finally made me “get” it. Everything is done very much “the Rails way”—a way that felt very unnatural to me before, but now after doing this book finally feels natural. This is also the only Rails book that does test-driven development the entire time, an approach highly recommended by the experts but which has never been so clearly demonstrated before. Finally, by including Git, GitHub, and Heroku in the demo examples, the author really gives you a feel for what it’s like to do a real-world project. The tutorial’s code examples are not in isolation.
The linear narrative is such a great format. Personally, I powered through the Rails Tutorial in three long days, doing all the examples and challenges at the end of each chapter. Do it from start to finish, without jumping around, and you’ll get the ultimate benefit.
Enjoy!
Derek Sivers (sivers.org)
Founder, CD Baby
Acknowledgments
The Ruby on Rails Tutorial owes a lot to my previous Rails book, RailsSpace, and hence to my coauthor Aurelius Prochazka. I’d like to thank Aure both for the work he did on that book and for his support of this one. I’d also like to thank Debra Williams Cauley, my editor on both RailsSpace and the Ruby on Rails Tutorial; as long as she keeps taking me to baseball games, I’ll keep writing books for her.
I’d like to acknowledge a long list of Rubyists who have taught and inspired me over the years: David Heinemeier Hansson, Yehuda Katz, Carl Lerche, Jeremy Kemper, Xavier Noria, Ryan Bates, Geoffrey Grosenbach, Peter Cooper, Matt Aimonetti, Gregg Pollack, Wayne E. Seguin, Amy Hoy, Dave Chelimsky, Pat Maddox, Tom Preston-Werner, Chris Wanstrath, Chad Fowler, Josh Susser, Obie Fernandez, Ian McFarland, Steven Bristol, Pratik Naik, Sarah Mei, Sarah Allen, Wolfram Arnold, Alex Chaffee, Giles Bowkett, Evan Dorn, Long Nguyen, James Lindenbaum, Adam Wiggins, Tikhon Bernstam, Ron Evans, Wyatt Greene, Miles Forrest, the good people at Pivotal Labs, the Heroku gang, the thoughtbot guys, and the GitHub crew. Finally, many, many readers—far too many to list—have contributed a huge number of bug reports and suggestions during the writing of this book, and I gratefully acknowledge their help in making it as good as it can be.
Michael Hartl is the author of the Ruby on Rails Tutorial, the leading introduction to web development with Ruby on Rails. His prior experience includes writing and developing RailsSpace, an extremely obsolete Rails tutorial book, and developing Insoshi, a once-popular and now-obsolete social networking platform in Ruby on Rails. In 2011, Michael received a Ruby Hero Award for his contributions to the Ruby community. He is a graduate of Harvard College, has a Ph.D. in Physics from Caltech, and is an alumnus of the Y Combinator entrepreneur program.
Copyright and license
Ruby on Rails Tutorial: Learn Web Development with Rails. Copyright © 2013 by Michael Hartl. All source code in the Ruby on Rails Tutorial is available jointly under the MIT License and the Beerware License.
The MIT License
Copyright (c) 2013 Michael Hartl
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, modify, 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 PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
/*
* ----------------------------------------------------------------------------
* "THE BEER-WARE LICENSE" (Revision 42):
* Michael Hartl wrote this code. As long as you retain this notice you
* can do whatever you want with this stuff. If we meet some day, and you think
* this stuff is worth it, you can buy me a beer in return.
* ----------------------------------------------------------------------------
*/
Chapter 1 From zero to deploy
Welcome to the Ruby on Rails Tutorial. The goal of this book is to be the best answer to the question, “If I want to learn web development with Ruby on Rails, where should I start?” By the time you finish the Ruby on Rails Tutorial, you will have all the skills you need to develop and deploy your own custom web applications with Rails. You will also be ready to benefit from the many more advanced books, blogs, and screencasts that are part of the thriving Rails educational ecosystem. Finally, since the Ruby on Rails Tutorial uses Rails 4, the knowledge you gain here represents the state of the art in web development. (The most up-to-date version of the Ruby on Rails Tutorial can be found on the book’s website at http://railstutorial.org/; if you are reading this book offline, be sure to check the online version of the Rails Tutorial book at http://railstutorial.org/book for the latest updates.)(Note: The present volume is the Rails 4.0 version of the book, which means that it has been revised to be compatible with Rails 4.0, but it is not yet a new edition because the changes in Rails don’t yet justify it. From the perspective of an introductory tutorial, the differences between Rails 4.0 and the previous version, Rails 3.2, are slight. Indeed, although there are a large number of miscellaneous small changes (Box 1.1), for our purposes there is only one significant difference, a new security technique called strong parameters, covered in Section 7.3.2. Once the changes in Rails justify the effort, I plan to prepare a full new edition of the Rails Tutorial, including coverage of topics such as Turbolinks and Russian doll caching, as well as some new aspects of RSpec, such as feature specs.)
It’s worth emphasizing that the goal of this book is not merely to teach Rails, but rather to teach web development with Rails, which means acquiring (or expanding) the skills needed to develop software for the World Wide Web. In addition to Ruby on Rails, this skillset includes HTML & CSS, databases, version control, testing, and deployment. To accomplish this goal, the Ruby on Rails Tutorial takes an integrated approach: you will learn Rails by example by building a substantial sample application from scratch. As Derek Sivers notes in the foreword, this book is structured as a linear narrative, designed to be read from start to finish. If you are used to skipping around in technical books, taking this linear approach might require some adjustment, but I suggest giving it a try. You can think of the Ruby on Rails Tutorial as a video game where you are the main character, and where you level up as a Rails developer in each chapter. (The exercises are the minibosses.)
In this first chapter, we’ll get started with Ruby on Rails by installing all the necessary software and by setting up our development environment (Section 1.2). We’ll then create our first Rails application, called (appropriately enough)
first_app. The Rails Tutorial
emphasizes good software development practices, so immediately after
creating our fresh new Rails project we’ll put it under version control
with Git (Section 1.3). And, believe it or not, in this chapter we’ll even put our first app on the wider web by deploying it to production (Section 1.4).In Chapter 2, we’ll make a second project, whose purpose is to demonstrate the basic workings of a Rails application. To get up and running quickly, we’ll build this demo app (called
demo_app) using scaffolding (Box 1.2) to generate code; since this code is both ugly and complex, Chapter 2 will focus on interacting with the demo app through its URIs (often called URLs)1 using a web browser.The rest of the tutorial focuses on developing a single large sample application (called
sample_app), writing all the code from scratch. We’ll develop the sample app using test-driven development (TDD), getting started in Chapter 3 by creating static pages and then adding a little dynamic content. We’ll take a quick detour in Chapter 4 to learn a little about the Ruby language underlying Rails. Then, in Chapter 5 through Chapter 9,
we’ll complete the foundation for the sample application by making a
site layout, a user data model, and a full registration and
authentication system. Finally, in Chapter 10 and Chapter 11 we’ll add microblogging and social features to make a working example site.The final sample application will bear more than a passing resemblance to a certain popular social microblogging site—a site which, coincidentally, was also originally written in Rails. Though of necessity our efforts will focus on this specific sample application, the emphasis throughout the Rails Tutorial will be on general principles, so that you will have a solid foundation no matter what kinds of web applications you want to build.
1.1 Introduction
Since its debut in 2004, Ruby on Rails has rapidly become one of the most powerful and popular frameworks for building dynamic web applications. Everyone from scrappy startups to huge companies have used Rails: 37signals, GitHub, Shopify, Scribd, Twitter, Disney, Hulu, the Yellow Pages—the list of sites using Rails goes on and on. There are also many web development shops that specialize in Rails, such as ENTP, thoughtbot, Pivotal Labs, and Hashrocket, plus innumerable independent consultants, trainers, and contractors.What makes Rails so great? First of all, Ruby on Rails is 100% open-source, available under the permissive MIT License, and as a result it also costs nothing to download or use. Rails also owes much of its success to its elegant and compact design; by exploiting the malleability of the underlying Ruby language, Rails effectively creates a domain-specific language for writing web applications. As a result, many common web programming tasks—such as generating HTML, making data models, and routing URLs—are easy with Rails, and the resulting application code is concise and readable.
Rails also adapts rapidly to new developments in web technology and framework design. For example, Rails was one of the first frameworks to fully digest and implement the REST architectural style for structuring web applications (which we’ll be learning about throughout this tutorial). And when other frameworks develop successful new techniques, Rails creator David Heinemeier Hansson and the Rails core team don’t hesitate to incorporate their ideas. Perhaps the most dramatic example is the merger of Rails and Merb, a rival Ruby web framework, so that Rails now benefits from Merb’s modular design, stable API, and improved performance.
Finally, Rails benefits from an unusually enthusiastic and diverse community. The results include hundreds of open-source contributors, well-attended conferences, a huge number of gems (self-contained solutions to specific problems such as pagination and image upload), a rich variety of informative blogs, and a cornucopia of discussion forums and IRC channels. The large number of Rails programmers also makes it easier to handle the inevitable application errors: the “Google the error message” algorithm nearly always produces a relevant blog post or discussion-forum thread.
1.1.1 Comments for various readers
The Rails Tutorial contains integrated tutorials not only for Rails, but also for the underlying Ruby language, the RSpec testing framework, HTML, CSS, a small amount of JavaScript, and even a little SQL. This means that, no matter where you currently are in your knowledge of web development, by the time you finish this tutorial you will be ready for more advanced Rails resources, as well as for the more systematic treatments of the other subjects mentioned. It also means that there’s a lot of material to cover; if you don’t already have much experience programming computers, you might find it overwhelming. The comments below contain some suggestions for approaching the Rails Tutorial depending on your background.All readers: One common question when learning Rails is whether to learn Ruby first. The answer depends on your personal learning style and how much programming experience you already have. If you prefer to learn everything systematically from the ground up, or if you have never programmed before, then learning Ruby first might work well for you, and in this case I recommend Beginning Ruby by Peter Cooper. On the other hand, many beginning Rails developers are excited about making web applications, and would rather not slog through a 500-page book on pure Ruby before ever writing a single web page. In this case, I recommend following the short interactive tutorial at Try Ruby,2 and then optionally do the free tutorial at Rails for Zombies3 to get a taste of what Rails can do.
Another common question is whether to use tests from the start. As noted in the introduction, the Rails Tutorial uses test-driven development (also called test-first development), which in my view is the best way to develop Rails applications, but it does introduce a substantial amount of overhead and complexity. If you find yourself getting bogged down by the tests, I suggest either skipping them on a first reading or (even better) using them as a tool to verify your code’s correctness without worrying about how they work. This latter strategy involves creating the necessary test files (called specs) and filling them with the test code exactly as it appears in the book. You can then run the test suite (as described in Chapter 5) to watch it fail, then write the application code as described in the tutorial, and finally re-run the test suite to watch it pass.
Inexperienced programmers: The Rails Tutorial is not aimed principally at beginning programmers, and web applications, even relatively simple ones, are by their nature fairly complex. If you are completely new to web programming and find the Rails Tutorial too difficult, I suggest learning the basics of HTML and CSS and then giving the Rails Tutorial another go. (Unfortunately, I don’t have a personal recommendation here, but Head First HTML looks promising, and one reader recommends CSS: The Missing Manual by David Sawyer McFarland.) You might also consider reading the first few chapters of Beginning Ruby by Peter Cooper, which starts with sample applications much smaller than a full-blown web app. That said, a surprising number of beginners have used this tutorial to learn web development, so I suggest giving it a try, and I especially recommend the Rails Tutorial screencast series4 to give you an “over-the-shoulder” look at Rails software development.
Experienced programmers new to web development: Your previous experience means you probably already understand ideas like classes, methods, data structures, etc., which is a big advantage. Be warned that if your background is in C/C++ or Java, you may find Ruby a bit of an odd duck, and it might take time to get used to it; just stick with it and eventually you’ll be fine. (Ruby even lets you put semicolons at the ends of lines if you miss them too much.) The Rails Tutorial covers all the web-specific ideas you’ll need, so don’t worry if you don’t currently know a POST from a PATCH.
Experienced web developers new to Rails: You have a great head start, especially if you have used a dynamic language such as PHP or (even better) Python. The basics of what we cover will likely be familiar, but test-driven development may be new to you, as may be the structured REST style favored by Rails. Ruby has its own idiosyncrasies, so those will likely be new, too.
Experienced Ruby programmers: The set of Ruby programmers who don’t know Rails is a small one nowadays, but if you are a member of this elite group you can fly through this book and then move on to developing applications of your own.
Inexperienced Rails programmers: You’ve perhaps read some other tutorials and made a few small Rails apps yourself. Based on reader feedback, I’m confident that you can still get a lot out of this book. Among other things, the techniques here may be more up-to-date than the ones you picked up when you originally learned Rails.
Experienced Rails programmers: This book is unnecessary for you, but many experienced Rails developers have expressed surprise at how much they learned from this book, and you might enjoy seeing Rails from a different perspective.
After finishing the Ruby on Rails Tutorial, I recommend that experienced programmers read The Well-Grounded Rubyist by David A. Black, Eloquent Ruby by Russ Olsen, or The Ruby Way by Hal Fulton, which is also fairly advanced but takes a more topical approach.
At the end of this process, no matter where you started, you should be ready for the many more intermediate-to-advanced Rails resources out there. Here are some I particularly recommend:
- RailsCasts by Ryan Bates: Excellent (mostly) free Rails screencasts
- PeepCode: Excellent commercial screencasts
- Code School: Interactive programming courses
- Rails Guides: Good topical and up-to-date Rails references
- RailsCasts by Ryan Bates: Did I already mention RailsCasts? Seriously: RailsCasts.
1.1.2 “Scaling” Rails
Before moving on with the rest of the introduction, I’d like to take a moment to address the one issue that dogged the Rails framework the most in its early days: the supposed inability of Rails to “scale”—i.e., to handle large amounts of traffic. Part of this issue relied on a misconception; you scale a site, not a framework, and Rails, as awesome as it is, is only a framework. So the real question should have been, “Can a site built with Rails scale?” In any case, the question has now been definitively answered in the affirmative: some of the most heavily trafficked sites in the world use Rails. Actually doing the scaling is beyond the scope of just Rails, but rest assured that if your application ever needs to handle the load of Hulu or the Yellow Pages, Rails won’t stop you from taking over the world.1.1.3 Conventions in this book
The conventions in this book are mostly self-explanatory. In this section, I’ll mention some that may not be.Both the HTML and PDF editions of this book are full of links, both to internal sections (such as Section 1.2) and to external sites (such as the main Ruby on Rails download page).5
Many examples in this book use command-line commands. For simplicity, all command line examples use a Unix-style command line prompt (a dollar sign), as follows:
$ echo "hello, world"
hello, world
>:C:\Sites> echo "hello, world"
hello, world
sudo, which stands for “substitute user do”.6 By default, a command executed with sudo
is run as an administrative user, which has access to files and
directories that normal users can’t touch, such as in this example from Section 1.2.2:$ sudo ruby setup.rb
sudo by default, unless you are using Ruby Version Manager as suggested in Section 1.2.2.3; in this case, you would type this instead:$ ruby setup.rb
$ rails server
/). My Rails Tutorial sample application, for instance, lives in/Users/mhartl/rails_projects/sample_app
C:\Sites\sample_app
config directory of my sample application is/Users/mhartl/rails_projects/sample_app/config
config, i.e.,/Users/mhartl/rails_projects/sample_app
/Users/mhartl/rails_projects/sample_app/config/routes.rb
config/routes.rb.The Rails Tutorial often shows output from various programs (shell commands, version control status, Ruby programs, etc.). Because of the innumerable small differences between different computer systems, the output you see may not always agree exactly with what is shown in the text, but this is not cause for concern.
Some commands may produce errors depending on your system; rather than attempt the Sisyphean task of documenting all such errors in this tutorial, I will delegate to the “Google the error message” algorithm, which among other things is good practice for real-life software development. If you run into any problems while following the tutorial, I suggest consulting the resources listed on the Rails Tutorial help page.7
1.2 Up and running
I think of Chapter 1 as the “weeding out phase” in law school—if you can get your dev environment set up, the rest is easy to get through.It’s time now to get going with a Ruby on Rails development environment and our first application. There is quite a bit of overhead here, especially if you don’t have extensive programming experience, so don’t get discouraged if it takes a while to get started. It’s not just you; every developer goes through it (often more than once), but rest assured that the effort will be richly rewarded.
—Bob Cavezza, Rails Tutorial reader
1.2.1 Development environments
Considering various idiosyncratic customizations, there are probably as many development environments as there are Rails programmers, but there are at least two broad types: text editor/command line environments, and integrated development environments (IDEs). Let’s consider the latter first.IDEs
The most prominent Rails IDEs are RadRails and RubyMine. I’ve heard especially good things about RubyMine, and one reader (David Loeffler) has assembled notes on how to use RubyMine with this tutorial.8 If you’re comfortable using an IDE, I suggest taking a look at the options mentioned to see what fits with the way you work.Text editors and command lines
Instead of using an IDE, I prefer to use a text editor to edit text, and a command line to issue commands (Figure 1.1). Which combination you use depends on your tastes and your platform.- Text editor: I recommend Sublime Text 2, an outstanding cross-platform text editor that is simultaneously easy to learn and industrial-strength.9 Sublime Text is heavily influenced by TextMate, and in fact is compatible with most TextMate customizations, such as snippets and color schemes. (TextMate, which is available only on OS X, is still a good choice if you use a Mac.) A second excellent choice is Vim,10 versions of which are available for all major platforms. Sublime Text can be obtained commercially, whereas Vim can be obtained at no cost; both are industrial-strength editors, but in my experience Sublime Text is much more accessible to beginners.
- Terminal: On OS X, I recommend either use iTerm or the native Terminal app. On Linux, the default terminal is fine. On Windows, many users prefer to develop Rails applications in a virtual machine running Linux, in which case your command-line options reduce to the previous case. If developing within Windows itself, I recommend using the command prompt that comes with Rails Installer (Section 1.2.2.1).
Figure 1.1: A text editor/command line development environment. (full size)
Browsers
Although there are many web browsers to choose from, the vast majority of Rails programmers use Firefox, Safari, or Chrome when developing. All three browsers include a built-in “Inspect element” feature available by right- (or control-)clicking on any part of the page.A note about tools
In the process of getting your development environment up and running, you may find that you spend a lot of time getting everything just right. The learning process for editors and IDEs is particularly long; you can spend weeks on Sublime Text or Vim tutorials alone. If you’re new to this game, I want to assure you that spending time learning tools is normal. Everyone goes through it. Sometimes it is frustrating, and it’s easy to get impatient when you have an awesome web app in your head and you just want to learn Rails already, but have to spend a week learning some weird ancient Unix editor just to get started. But, as with an apprentice carpenter striving to master the chisel or the plane, there is no subsitute for mastering the tools of your trade, and in the end the reward is worth the effort.1.2.2 Ruby, RubyGems, Rails, and Git
Practically all the software in the world is either broken or very difficult to use. So users dread software. They’ve been trained that whenever they try to install something, or even fill out a form online, it’s not going to work. I dread installing stuff, and I have a Ph.D. in computer science.Now it’s time to install Ruby and Rails. I’ve done my best to cover as many bases as possible, but systems vary, and many things can go wrong during these steps. Be sure to Google the error message or consult the Rails Tutorial help page if you run into trouble. Also, there’s a new resource called Install Rails from One Month Rails that might help you if you get stuck.
—Paul Graham, in Founders at Work by Jessica Livingston
Unless otherwise noted, you should use the exact versions of all software used in the tutorial, including Rails itself, if you want the same results. Sometimes minor version differences will yield identical results, but you shouldn’t count on this, especially with respect to Rails versions. The main exception is Ruby itself: 1.9.3 and 2.0.0 are virtually identical for the purposes of this tutorial, so feel free to use either one.
Rails Installer (Windows)
Installing Rails on Windows used to be a real pain, but thanks to the efforts of the good people at Engine Yard—especially Dr. Nic Williams and Wayne E. Seguin—installing Rails and related software on Windows is now easy. If you are using Windows, go to Rails Installer and download the Rails Installer executable and view the excellent installation video. Double-click the executable and follow the instructions to install Git (so you can skip Section 1.2.2.2), Ruby (skip Section 1.2.2.3), RubyGems (skip Section 1.2.2.4), and Rails itself (skip Section 1.2.2.5). Once the installation has finished, you can skip right to the creation of the first application in Section 1.2.3.Bear in mind that the Rails Installer might use a slightly different version of Rails from the one installed in Section 1.2.2.5, which might cause incompatibilities. To fix this, I am currently working with Nic and Wayne to create a list of Rails Installers ordered by Rails version number.
Install Git
Much of the Rails ecosystem depends in one way or another on a version control system called Git (covered in more detail in Section 1.3). Because its use is ubiquitous, you should install Git even at this early stage; I suggest following the installation instructions for your platform at the Installing Git section of Pro Git.Install Ruby
The next step is to install Ruby. (This can be painful and error-prone, and I actually dread having to install new versions of Ruby, but unfortunately it’s the cost of doing business.)It’s possible that your system already has Ruby installed. Try running
$ ruby -v
As part of installing Ruby, if you are using OS X or Linux I strongly recommend using Ruby Version Manager (RVM) or rbenv, which allow you to install and manage multiple versions of Ruby on the same machine. (The Pik project accomplishes a similar feat on Windows.) This is particularly important if you want to run different versions of Ruby or Rails on the same machine. Unfortunately, RVM and rbenv can’t be used on the same system simultaneously, and since I’ve been using RVM longer that’s the one I use in this tutorial. I hear great things about rbenv, though, so you should feel free to use that if you already know it or if you have access to a local rbenv expert.
As a prerequisite, OS X users may need to install the Xcode developer tools. To avoid the (huge) full installation, I recommend the much smaller Command Line Tools for Xcode.12
To get started with the Ruby installation, first install RVM:
$ curl -L https://get.rvm.io | bash -s
$ rvm get stable
You can then get Ruby set up by examining the requirements for installing it:
$ rvm requirements
$ brew install libtool libxslt libksba openssl
apt-get or yum.I also had to install a YAML library:
# For Mac with Homebrew
$ brew install libyaml
# For Debian-based Linux systems
$ apt-get install libyaml-dev
# For Fedora/CentOS/RHEL Linux systems
$ yum install libyaml-devel
$ rvm install 2.0.0 --with-openssl-dir=$HOME/.rvm/usr
<wait a while>
$ rvm install 2.0.0 --with-openssl-dir=$HOME/.rvm/opt/openssl
<wait a while>
After installing Ruby, you should configure your system for the other software needed to run Rails applications. This typically involves installing gems, which are self-contained packages of Ruby code. Since gems with different version numbers sometimes conflict, it is often convenient to create separate gemsets, which are self-contained bundles of gems. For the purposes of this tutorial, I suggest creating a gemset called
railstutorial_rails_4_0:$ rvm use 2.0.0@railstutorial_rails_4_0 --create --default
Using /Users/mhartl/.rvm/gems/ruby-2.0.0-p0 with gemset railstutorial_rails_4_0
railstutorial_rails_4_0 associated with Ruby 2.0.0 while arranging to start using it immediately (use) and setting it as the default (--default) gemset, so that any time we open a new terminal window the 2.0.0@railstutorial_rails_4_0
Ruby/gemset combination is automatically selected. RVM supports a large
variety of commands for manipulating gemsets; see the documentation at http://rvm.beginrescueend.com/gemsets/. If you ever get stuck with RVM, running commands like these should help you get your bearings:$ rvm help
$ rvm gemset help
Install RubyGems
RubyGems is a package manager for Ruby projects, and there are many useful libraries (including Rails) available as Ruby packages, or gems. Installing RubyGems should be easy once you install Ruby. In fact, if you have installed RVM, you already have RubyGems, since RVM includes it automatically:$ which gem
/Users/mhartl/.rvm/rubies/ruby-2.0.0-p0/bin/gem
rubygems directory and run the setup program:$ ruby setup.rb
sudo.)If you already have RubyGems installed, you should make sure your system uses the version used in this tutorial:
$ gem update --system 2.1.9
When installing gems, by default RubyGems generates two different kinds of documentation (called ri and rdoc), but many Ruby and Rails developers find that the time to build them isn’t worth the benefit. (Many programmers rely on online documentation instead of the native ri and rdoc documents.) To prevent the automatic generation of the documentation, I recommend making a gem configuration file called
.gemrc in your home directory as in Listing 1.1 with the line in Listing 1.2. (The tilde “~” means “home directory”, while the dot . in .gemrc makes the file hidden, which is a common convention for configuration files. )
Listing 1.1. Creating a gem configuration file.
$ subl ~/.gemrc
subl is the command-line command to launch Sublime Text on OS X, which you can set up using the Sublime Text 2 documentation for the OS X command line.
If you’re on a different platform, or if you’re using a different
editor, you should replace this command as necessary (i.e., by
double-clicking the application icon or by using an alternate command
such as mate, vim, gvim, or mvim). For brevity, throughout the rest of this tutorial I’ll use subl as a shorthand for “open with your favorite text editor.”
Listing 1.2. Suppressing the ri and rdoc documentation in
.gemrc. install: --no-rdoc --no-ri
update: --no-rdoc --no-ri
Install Rails
Once you’ve installed RubyGems, installing Rails should be easy. This tutorial standardizes on Rails 4.0, which we can install as follows:$ gem install rails --version 4.0.2
$ rails -v
Rails 4.0.2
If you’re running Linux, you might have to install a couple of other packages at this point:
$ sudo apt-get install libxslt-dev libxml2-dev libsqlite3-dev # Linux only
1.2.3 The first application
Virtually all Rails applications start the same way, by runningrails new
command. This handy command creates a skeleton Rails application in a
directory of your choice. To get started, make a directory for your
Rails projects and then run rails new to make the first application (Listing 1.3):
Listing 1.3. Running
rails new to generate a new application. $ mkdir rails_projects
$ cd rails_projects
$ rails new first_app
create
create README.rdoc
create Rakefile
create config.ru
create .gitignore
create Gemfile
create app
create app/assets/javascripts/application.js
create app/assets/stylesheets/application.css
create app/controllers/application_controller.rb
.
.
.
create test/test_helper.rb
create tmp/cache
create tmp/cache/assets
create vendor/assets/javascripts
create vendor/assets/javascripts/.keep
create vendor/assets/stylesheets
create vendor/assets/stylesheets/.keep
run bundle install
.
.
.
Your bundle is complete! Use `bundle show [gemname]` to see where a bundled
gem is installed.
rails new automatically runs the bundle install command after the file creation is done. If that step doesn’t work right now, don’t worry; follow the steps in Section 1.2.4 and you should be able to get it to work.Notice how many files and directories the
rails command creates. This standard directory and file structure (Figure 1.2)
is one of the many advantages of Rails; it immediately gets you from
zero to a functional (if minimal) application. Moreover, since the
structure is common to all Rails apps, you can immediately get your
bearings when looking at someone else’s code. A summary of the default
Rails files appears in Table 1.1; we’ll learn about most of these files and directories throughout the rest of this book. In particular, starting in Section 5.2.1 we’ll discuss the app/assets directory, part of the asset pipeline that makes it easier than ever to organize and deploy assets such as cascading style sheets and JavaScript files.
Figure 1.2: The directory structure for a newly created Rails app. (full size)
| File/Directory | Purpose |
|---|---|
app/ | Core application (app) code, including models, views, controllers, and helpers |
app/assets | Applications assets such as cascading style sheets (CSS), JavaScript files, and images |
bin/ | Binary executable files |
config/ | Application configuration |
db/ | Database files |
doc/ | Documentation for the application |
lib/ | Library modules |
lib/assets | Library assets such as cascading style sheets (CSS), JavaScript files, and images |
log/ | Application log files |
public/ | Data accessible to the public (e.g., web browsers), such as error pages |
bin/rails | A program for generating code, opening console sessions, or starting a local server |
test/ | Application tests (made obsolete by the spec/ directory in Section 3.1) |
tmp/ | Temporary files |
vendor/ | Third-party code such as plugins and gems |
vendor/assets | Third-party assets such as cascading style sheets (CSS), JavaScript files, and images |
README.rdoc | A brief description of the application |
Rakefile | Utility tasks available via the rake command |
Gemfile | Gem requirements for this app |
Gemfile.lock | A list of gems used to ensure that all copies of the app use the same gem versions |
config.ru | A configuration file for Rack middleware |
.gitignore | Patterns for files that should be ignored by Git |
Table 1.1: A summary of the default Rails directory structure.
1.2.4 Bundler
After creating a new Rails application, the next step is to use Bundler to install and include the gems needed by the app. As noted briefly in Section 1.2.3, Bundler is run automatically (viabundle install) by the rails
command, but in this section we’ll make some changes to the default
application gems and run Bundler again. This involves opening the Gemfile with your favorite text editor:$ cd first_app/
$ subl Gemfile
Listing 1.4. The default
Gemfile in the first_app directory. source 'https://rubygems.org'
# Use sqlite3 as the database for Active Record
gem 'sqlite3'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.1'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'
# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby
# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes following links in your web application faster.
# Read more: https://github.com/rails/turbolinks
gem 'turbolinks'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 1.0.1'
group :doc do
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', require: false
end
# Use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.1.2'
# Use unicorn as the app server
# gem 'unicorn'
# Use Capistrano for deployment
# gem 'capistrano', group: :development
# Use debugger
# gem 'debugger', group: [:development, :test]
#;
they are there to show you some commonly needed gems and to give
examples of the Bundler syntax. For now, we won’t need any gems other
than the defaults.Unless you specify a version number to the
gem command,
Bundler will automatically install the latest version of the gem.
Unfortunately, gem updates often cause minor but potentially confusing
breakage, so in this tutorial we’ll include explicit version numbers
known to work, as seen in Listing 1.5 (which also omits the commented-out lines from Listing 1.4).
Listing 1.5. A
Gemfile with an explicit version for each Ruby gem. source 'https://rubygems.org'
ruby '2.0.0'
#ruby-gemset=railstutorial_rails_4_0
gem 'rails', '4.0.2'
group :development do
gem 'sqlite3', '1.3.8'
end
gem 'sass-rails', '4.0.1'
gem 'uglifier', '2.1.1'
gem 'coffee-rails', '4.0.1'
gem 'jquery-rails', '3.0.4'
gem 'turbolinks', '1.1.1'
gem 'jbuilder', '1.0.2'
group :doc do
gem 'sdoc', '0.3.20', require: false
end
ruby '2.0.0'
#ruby-gemset=railstutorial_rails_4_0
#,
which is the Ruby comment character, it will be ignored if you aren’t
using RVM, but if you are RVM will conveniently use the right Ruby
version/gemset combination upon entering the application directory. (If
you are using a version of Ruby other than 2.0.0, you should change the
Ruby version line accordingly.)The updated
Gemfile also changes the line for jQuery, the default JavaScript library used by Rails, fromgem 'jquery-rails'
gem 'jquery-rails', '3.0.4'
gem 'sqlite3'
group :development do
gem 'sqlite3', '1.3.8'
end
1.3.8 of the sqlite3 gem. Note that we’ve also taken this opportunity to arrange for the gem to be included only in a development environment (Section 7.1.1), which prevents potential conflicts with the database used by Heroku (Section 1.4).Listing 1.5 also changes a few other lines, converting
# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'
gem 'sass-rails', '4.0.1'
gem 'uglifier', '2.1.1'
gem 'coffee-rails', '4.0.1'
gem 'uglifier', '>= 1.3.0'
uglifier gem (which handles file compression for the asset pipeline) as long as it’s greater than or equal to version 1.3.0—even if it’s, say, version 7.2. Meanwhile, the codegem 'coffee-rails', '~> 4.0.0'
coffee-rails (also needed by the asset pipeline) as long as it’s newer than version 4.0.0 but not newer than 4.1. In other words, the >= notation always installs the latest gem when you run bundle install, whereas the ~> 4.0.0 notation only installs updated gems representing minor point releases (e.g., from 4.0.0 to 4.0.1), but not major point releases (e.g., from 4.0 to 4.1). Unfortunately, experience shows that even minor point releases can break things, so for the Rails Tutorial we’ll err on the side of caution by including exact version numbers for virtually all gems.
You are welcome to use the most up-to-date version of any gem, including using the ~> construction in the Gemfile (which I generally recommend for more advanced users), but be warned that this may cause the tutorial to act unpredictably.Once you’ve assembled the proper
Gemfile, install the gems using
bundle update14 and bundle install:$ bundle update
$ bundle install
Fetching source index for https://rubygems.org/
.
.
.
bundle install command might take a few moments, but when it’s done our application will be ready to run.1.2.5 rails server
Thanks to runningrails new in Section 1.2.3 and bundle install in Section 1.2.4, we already have an application we can run—but how? Happily, Rails comes with a command-line program, or script, that runs a local web server, visible only from your development machine:$ rails server
=> Booting WEBrick
=> Rails application starting on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
0.0.0.0.
This address tells the computer to listen on every available IP address
configured on that specific machine; in particular, we can view the
application using the special address 127.0.0.1, which is also known as localhost. We can see the result of visiting http://localhost:3000/ in Figure 1.3.
Figure 1.3: The default Rails page. (full size)
Figure 1.4: The default page with the app environment. (full size)
1.2.6 Model-view-controller (MVC)
Even at this early stage, it’s helpful to get a high-level overview of how Rails applications work (Figure 1.5). You might have noticed that the standard Rails application structure (Figure 1.2) has an application directory calledapp/ with three subdirectories: models, views, and controllers. This is a hint that Rails follows the model-view-controller
(MVC) architectural pattern, which enforces a separation between
“domain logic” (also called “business logic”) from the input and
presentation logic associated with a graphical user interface (GUI). In
the case of web applications, the “domain logic” typically consists of
data models for things like users, articles, and products, and the GUI
is just a web page in a web browser.When interacting with a Rails application, a browser sends a request, which is received by a web server and passed on to a Rails controller, which is in charge of what to do next. In some cases, the controller will immediately render a view, which is a template that gets converted to HTML and sent back to the browser. More commonly for dynamic sites, the controller interacts with a model, which is a Ruby object that represents an element of the site (such as a user) and is in charge of communicating with the database. After invoking the model, the controller then renders the view and returns the complete web page to the browser as HTML.
Figure 1.5: A schematic representation of the model-view-controller (MVC) architecture.
from http://ruby.railstutorial.org/ruby-on-rails-tutorial-book