Wednesday, April 12, 2006

Ruby on Rails Framework

, often called RoR or just Rails, is an open source web application framework written in Ruby that closely follows the Model-View-Controller (MVC) architecture.

It strives for simplicity and allowing real-world applications to be developed in less code than other frameworks and with a minimum of configuration.

The Ruby programming language allows for extensive metaprogramming, which Rails makes much use of. This results in a very readable syntax, in the opinion of many of its users.

Rails is primarily distributed through RubyGems, which is the official packaging format and distribution channel for Ruby libraries and applications.


History

Ruby on Rails was extracted from Basecamp, a project-management tool, by 37signals. It was first released to the public in July 2004.

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Rails' MVC architecture

The pieces of the Model-View-Controller (MVC) architecture in Ruby on Rails are as follows:

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Model

In object-oriented, database-driven MVC web applications, Model consists of the classes representing RDBMS tables.

In Ruby on Rails, Model classes are handled through the Active Record. Usually, all the programmer needs to do is to subclass the ActiveRecord::Base class, and the program will automatically figure out which RDBMS table to use and what columns the table has.

The class definitions also specify the relations between classes with object-relational mapping commands. For example, if the class name Image has a definition has_many :comments, and there is an instance of Image named a, then a.comments will return an array with all Comment objects with image_id equal to a.id.

The data validation handlers (e.g. validates_uniqueness_of :checksum) and any update-related handlers (e.g. after_destroy :remove_file, before_update :update_related_details) are also specified and implemented in the model class.

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View

In MVC, View is the display logic, or how the data from the Controller classes is displayed. In web applications, this frequently consists of a minimal amount of code, interspersed in HTML.

There are currently many ways the views can be handled – the underlying view code is part of the Action Pack. The method in Rails itself is to use Embedded Ruby (.rhtml files), which are basically fragments of HTML with some Ruby code interspersed, with syntax quite similar to JSP. HTML and XML can also be constructed programmatically with Builder or through Liquid template system.

For each method in the controller that needs to display user output, a small HTML code fragment needs to be written. The page layout is described separately from the controller action that displays layouts, and the fragments can also call other fragments.

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Controller

In MVC, Controller classes respond to user interaction and call the application logic, which in turn manipulates the data in Model and displays the data through View. In web-based MVC applications, the Controller methods are initiated by the user through the web browser.

Controller implementation is handled through Rails' Action Pack, which contains the class ApplicationController. Rails applications simply subclass ApplicationController and write required actions as methods, which can then be accessed through the web, typically in form of /example/method, which calls ExampleController#method, and presents the data using the view file /app/views/example/method.rhtml, unless the method redirects elsewhere.

Rails also provides out-of-the-box scaffolding, which can quickly construct most of the logic and views needed to do common operations, such as CRUD.

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Other modules

In addition to this, Rails also offers some other modules, like Action Mailer for sending email and Action Web Service for SOAP and XML-RPC support.

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Ajax on Rails

A separate technology called Ajax, which allows for using JavaScript and XML to process queries by a web browser to a webserver as background processing without loading additional webpages, has been combined with this technology to produce a system referred to as "Ajax on Rails." Rails provides several helpers that make implementing Ajax applications easier.

Rails is host to both the Prototype JavaScript framework, a toolkit providing for Ajax calls and other functionality for often occurring client-side programming tasks, and script.aculo.us, a JavaScript library for user interface enhancement (advanced form controls, visual effects, drag and drop).

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Web server support

For development and testing, the lightweight WEBrick web server included with Ruby is often used as the application server. For production use, Apache or Lighttpd with FastCGI is recommended, but any web server with CGI or FastCGI support will work. On Apache, mod_ruby can help with performance considerably, though its use is frequently discouraged because it is unsafe to share multiple RoR applications on Apache. [1]

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Database support

Since the Rails architecture strongly favors database use, an RDBMS system is recommended for data storage, but Rails also supports the SQLite library if running an RDBMS server is not possible. The database access is entirely abstracted from programmer's point of view, and Rails handles access to all databases automatically – though, if needed, using direct SQL queries is possible. Rails attempts to maintain database-neutrality, application portability over different database systems, and usability of pre-existing databases for Rails application development as much as possible, though due to different feature sets of the RDBMSes, it is not completely guaranteed by the framework alone. Several different RDBMS systems are supported, including MySQL, PostgreSQL, SQLite, IBM DB2, Oracle and Microsoft SQL Server.

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Projects Using Ruby on Rails

Major software projects written using Ruby on Rails include:

Some major websites and services that are implemented on top of Ruby on Rails include:

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Requirements

  • Web server such as Apache 1.3.x or 2.x, lighttpd, or any FastCGI-capable webserver with a mod_rewrite-like module. For development, Rails' "server" script uses WEBrick, which may be used in place of other web servers. However, WEBrick generally exhibits slow performance and is not recommended for production use.
  • FastCGI for production performance. CGI is possible but quite slow. Rails supports Apache's mod_ruby.
  • Database and driver (e.g. MySQL, PostgreSQL, or SQLite)
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See also

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External links

posted by Socheat Yi @ 6:24 AM

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