Ruby on Rails

Original author(s)	David Heinemeier Hansson
Developer(s)	Rails Core Team
Stable release	3.2.13 / March 18, 2013 (2013-03-18)[1]
Preview release	4.0 RC 1 / May 1, 2013 (2013-05-01)[2]
Development status	Active
Written in	Ruby
Operating system	Cross-platform
Type	Web application framework
License	MIT License
Website	rubyonrails.org

Ruby on Rails, often simply Rails, is an open source web application framework which runs on the Ruby programming language. It is a full-stack framework: it allows creating pages and applications that gather information from the web server, talk to or query the database, and render templates out of the box. As a result, Rails features a routing system that is independent of the web server.

Ruby on Rails emphasizes the use of well-known software engineering patterns and principles, such as active record pattern, convention over configuration, don't repeat yourself, and model-view-controller.

History [edit]

David Heinemeier Hansson extracted Ruby on Rails from his work on Basecamp, a project management tool by 37signals (now a web application company).^[3] Hansson first released Rails as open source in July 2004, but did not share commit rights to the project until February 2005.^[4] In August 2006, the framework reached a milestone when Apple announced that it would ship Ruby on Rails with Mac OS X v10.5 "Leopard",^[5] which was released in October 2007.

Rails version 2.3 was released on March 15, 2009 with major new developments in templates, engines, Rack and nested model forms. Templates enable the developer to generate a skeleton application with custom gems and configurations. Engines give developers the ability to reuse application pieces complete with routes, view paths and models. The Rack web server interface and Metal allow one to write optimized pieces of code that route around ActionController.^[6]

On December 23, 2008, Merb, another web application framework, was launched, and Ruby on Rails announced it would work with the Merb project to bring "the best ideas of Merb" into Rails 3, ending the "unnecessary duplication" across both communities.^[7] Merb was merged with Rails as part of the Rails 3.0 release.^[8][9]

Rails 3.1 was released on August 31, 2011, featuring Reversible Database Migrations, Asset Pipeline, Streaming, jQuery as default JavaScript library and newly introduced CoffeeScript and Sass into the stack.^[10]

Rails 3.2 was released on January 20, 2012 with a faster development mode and routing engine (also known as Journey engine), Automatic Query Explain and Tagged Logging.^[11] Rails 3.2.x is the last version that supports Ruby 1.8.7.^[12]

Technical overview [edit]

Like many web frameworks, Ruby on Rails uses the Model-View-Controller (MVC) architecture pattern to organize application programming.

In a default configuration, a model in the Ruby on Rails framework maps to a table in a database, and a Ruby file. For example, a model class User will usually be defined in the file user.rb in the app/models directory, and is linked to the table users in the database. Developers can choose any model name, file name or database table name. But this is not common practice and usually discouraged according to the "convention over configuration" philosophy.

A controller is a component of Rails that responds to external requests from the web server to the application by determining which view file to render. The controller may also have to query one or more models directly for information and pass these on to the view. A controller may provide one or more actions. In Ruby on Rails, an action is typically a basic unit that describes how to respond to a specific external web-browser request. Also note that, only if a controller/action is mapped to the Rails router, will the controller/action be accessible for external web requests. Rails encourages developers to use RESTful routes, which include actions such as: create, new, edit, update, destroy, show, and index. These can be easily routed in the routes file.^{[clarification needed]}

A view in the default configuration of Rails is an erb file, which is converted to HTML at run-time. Many other templating systems can be used for views.

Ruby on Rails includes tools that make common development tasks easier "out of the box", such as scaffolding that can automatically construct some of the models and views needed for a basic website.^[23] Also included are WEBrick, a simple Ruby web server that is distributed with Ruby, and Rake, a build system, distributed as a gem. Together with Ruby on Rails, these tools provide a basic development environment.

Ruby on Rails is most commonly not connected to the Internet directly, but through some front-end web server. Mongrel was generally preferred over WEBrick in the early days,^{[citation needed]} but it can also run on Lighttpd, Apache, Cherokee, Hiawatha, nginx (either as a module — Phusion Passenger for example — or via CGI, FastCGI or mod_ruby), and many others. From 2008 onwards, the Passenger web server replaced Mongrel as the most-used web server for Ruby on Rails.^[24]

Ruby on Rails is also noteworthy for its extensive use of the JavaScript libraries Prototype and Script.aculo.us for Ajax.^[25] Ruby on Rails initially utilized lightweight SOAP for web services; this was later replaced by RESTful web services. Ruby on Rails 3.0 uses a technique called Unobtrusive JavaScript to separate the functionality (or logic) from the structure of the web page. jQuery is fully supported as a replacement for Prototype and is the default JavaScript library in Rails 3.1, reflecting an industry-wide move towards jQuery. Additionally, CoffeeScript was introduced in Rails 3.1 as the default Javascript language.

Since version 2.0, Ruby on Rails offers both HTML and XML as standard output formats. The latter is the facility for RESTful web services.

Rails 3.1 introduced Sass as standard CSS templating.

By default, the server uses Embedded Ruby in the HTML views, with files having an html.erb extension. Rails supports swapping-in alternative templating languages, such as HAML and Mustache.

Ruby on Rails 3.0 has been designed to work with Ruby 1.8.7, Ruby 1.9.2, and JRuby 1.5.2+; earlier versions are not supported.^[26]

Rails 3.2 series is the last series to support Ruby 1.8.7.

Framework structure [edit]

Ruby on Rails is separated into various packages, namely ActiveRecord (an object-relational mapping system for database access), ActiveResource (provides web services), ActionPack, ActiveSupport and ActionMailer. Prior to version 2.0, Ruby on Rails also included the Action Web Service package that is now replaced by Active Resource. Apart from standard packages, developers can make plugins to extend existing packages. Rails 3.2 deprecates the old plugins Rails 2-3-stable style in which plugins are to be placed under vendor/plugins, in favor of packaged gems.^[27]

Deployment [edit]

Ruby on Rails is often installed using RubyGems, a package manager^[28] which is included with current versions of Ruby. Many free Unix-like systems also support installation of Ruby on Rails and its dependencies through their native package management system.

Ruby on Rails is typically deployed with a database server such as MySQL or PostgreSQL, and a web server such as Apache running the Phusion Passenger module.

There are many Ruby on Rails web hosting services such as Heroku, Engine Yard and TextDrive.

Philosophy and design [edit]

Ruby on Rails is intended to emphasize Convention over Configuration (CoC), and the rapid development principle of Don't Repeat Yourself (DRY).

"Convention over Configuration" means a developer only needs to specify unconventional aspects of the application. For example, if there is a class Sale in the model, the corresponding table in the database is called sales by default. It is only if one deviates from this convention, such as calling the table "products sold", that the developer needs to write code regarding these names. Generally, Ruby on Rails conventions lead to less code and less repetition.^{[citation needed]}

"Don't repeat yourself" means that information is located in a single, unambiguous place. For example, using the ActiveRecord module of Rails, the developer does not need to specify database column names in class definitions. Instead, Ruby on Rails can retrieve this information from the database based on the class name.

"Fat models, skinny controllers" means that most of the application logic should be placed within the model while leaving the controller as light as possible.

Trademarks [edit]

In March 2007, David Heinemeier Hansson filed three Ruby on Rails related trademark applications to the USPTO. These applications regard the phrase "RUBY ON RAILS",^[29] the word "RAILS",^[30] and the official Rails logo.^[31] As a consequence, in the summer of 2007, Hansson denied permission to Apress to use the Ruby on Rails logo on the cover of a new Ruby on Rails book written by some authoritative community members. The episode gave rise to a polite protest in the Ruby on Rails community.^[32][33] In response to this criticism, Hansson replied:

I only grant promotional use [of the Rails logo] for products I'm directly involved with. Such as books that I've been part of the development process for or conferences where I have a say in the execution. I would most definitely seek to enforce all the trademarks of Rails.^[32]

Reception [edit]

Rails running on Matz's Ruby Interpreter (the de facto reference interpreter for Ruby) had been criticized for issues with scalability.^[34] These critics often mentioned various Twitter outages in 2007 and 2008, which spurred Twitter's partial transition to Scala (which runs on the Java Virtual Machine) for their queueing system and other middleware.^[35][36] The user interface aspects of the site continue to run Ruby on Rails.^[37]

In 2011, Gartner Research noted that despite criticisms and comparisons to Java, many high-profile consumer web firms are using Ruby on Rails to build agile, scalable web applications. Some of the largest sites running Ruby on Rails include Github, Yammer, Scribd, Groupon, Shopify, and Basecamp.^[38] As of March 2013, it is estimated that about 211,295 web sites are running Ruby on Rails.^[39]

See also [edit]

Computer programming portal

• Comparison of web application frameworks

References [edit]

Bibliography [edit]

External links [edit]

Wikibooks has a book on the topic of: Ruby on Rails

• Ruby on Rails official website, rubyonrails.org
• Railscasts.com, These screencasts are short and focus on Ruby on Rails technique
• Rails source code