Rails

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Rails
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What is Rails?

• Rails is a framework for building web
  applications
• This involves
• Getting information from the user (client), using
  HTML forms
• Doing validation
• Maintaining session information
• Managing a database
• Displaying results to the user
• Rails differs from similar frameworks in C or
  Java
• Rails applications can be built much more quickly
• Rails requires knowledge of fewer technologies

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Required software

• You need
• The Ruby language
• A database, such as MySQL
• A Ruby-capable web server, such as lightppd,
  WEBRick, or Mongrel
• On Windows, InstantRails provides all of these
• On Macintosh, Locomotive provides these
• On Linux you probably have to assemble the pieces
  yourself
• Its also helpful to have
• A good text editor, such as TextMate or TextPad
• A Ruby IDE, such as Eclipse with the RDT plugin,
  or RadRails
• A GUI interface for looking at your database

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Rails philosophy

• Convention over configuration
• Other frameworks use several XML configuration
  files to specify where everything is, and how the
  parts are related
• Rails assumes a standard configuration.
• Don't Repeat Yourself (DRY)
• Every piece of information (program or data)
  should be represented once and only once
• Rails provides a structure that encourages DRY
• Agile development
• In Rails we start with a working program and
  grow it by making small changes
• In Rails it is easy to re-test after every small
  change
• Rails provides strong support for unit testing

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Three environments

• By default, Rails projects use three environments
• The development environment
• Classes are reloaded after every change, so every
  change you make happens immediately--you dont
  have to restart the server
• This is where you do most of your work
• The test environment
• Classes are also reloaded after every change
• For each test, Rails creates a fresh copy of the
  data in the test database
• The production environment
• Classes are only loaded once
• Changes typically require stopping and restarting
  the server
• The environment is tuned for speed

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Starting an application

• To create a new application, such as the Cookbook
  application in the Curt Hibbs example, enter the
  command rails cookbook
• This creates a directory (folder) named cookbook
  and, beneath it, a large directory structure and
  a number of files

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The directories, I

• Rails creates the following subdirectories of the
  cookbook directory
• app -- more about this directory later
• components -- reusable components
• config -- configuration information, including
  database connection parameters
• db -- database schema information
• doc -- autogenerated documentation
• lib -- code produced by your company and shared
  by many applications
• vendor -- purchased code shared by many
  applications

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The directories, II

• More subdirectories
• log -- log files produced by the application
• public -- the web-accessible directory your
  program appears to be running from here
• Rakefile -- scripts for creating documentation
  and tests
• script -- utility scripts
• tests -- unit tests, functional tests, mocks, and
  fixtures
• Of these, the app subdirectory is the most
  important, but you will probably also use the
  config, db, and test directories