Rails Introduction

Kung-Fu

Installation

• Windows – InstantRails one-click installer
• Mac – Ruby 1.8.6 is pre-installed on Mac as of 10.4.6 (Tiger). Rails 1.2.6 is pre-installed on Mac 10.5.
• Linux – there are packages for most distributions
• Editors: TextMate (OS X), E Text Editor (Windows), jEdit, SciTE, RadRails, NetBeans, 3rdRail, IntelliJ IDEA, vim, Emacs

Rails Background

• Jason Fried + David Heinemeier Hanson => BaseCamp, Ruby on Rails
• Java, PHP => Ruby
• Hottest Hacker on the Earth, Best Hacker of the year 2005, Jolt Awards 2006
• Getting Real – Less is More
• Dave Thomas and the Pragmatic Programmers

Rails Elevator Pitch

Rails Philosophy and Strengths

• Ruby – less and more readable code, shorter development times, simple but powerful, no compilation cycle
• Convention over configuration => almost no config files, predefined directory structure, naming conventions => less code, easier maintenance
• Best practices: MVC, DRY, Testing
• Almost everything in Rails is Ruby code (SQL and JavaScript are abstracted)
• Integrated AJAX support. Web services with REST.
• Good community, tools, and documentation
• Extracted from a real application

MVC Request Cycle

Building a Demo Application

Directory Structure

app
      controllers
      helpers
      models
      views
        layouts
config
      environment.rb
      routes.rb
db
      database.yml
      migrations
lib
log
public  
script
test
vendor
  plugins
  gems
  rails

MVC Request Cycle in Detail

1. A request is made from the browser to the URL http://localhost:3000/users/show/1.
2. A Rails server running locally on port 3000 receives the request and the dispatcher is invoked. Rails tries to find a route (in the file config/routes.rb) to match the URI /users/show/1. The default route ’:controller/:action/:id’ matches the URI and the dispatcher instantiates the users controller and invokes its show method with the :id parameter set to 1.
3. The show method in the users controller fetches the user model object from the database with id equal to 1.
4. The show method renders its view (the file show.rhtml) which generates an HTML page with the user info from the user model object.
5. Rails sends the generated HTML from the view back to the browser.

Rake

• Rake lets you define a dependency tree of tasks to be executed.
• Rake tasks are loaded from the file Rakefile
• Rails rake tasks live under railties/lib/tasks
• You can put your own tasks under lib/tasks

Useful Rake Tasks

• db:migrate
• db:sessions:create
• doc:app
• doc:rails
• log:clear
• rails:freeze:gems
• rails:freeze:edge
• test (default task)
• stats

script/*

• about
• console
• dbconsole
• generate/destroy
• plugin
• runner
• server

Environments

• Rails ships with three environments: development, test, and production
• Every environment has a database connection in config/database.yml and a configuration file under config/environments.
• It’s easy to add custom environments, i.e. for a staging server
• Rails always runs in only one environment, dictated by ENV[‘RAILS_ENV’] (same as RAILS_ENV and Rails.env)

config/environment.rb and config/initializers

• log level
• how sessions are stored
• schema format
• gem dependencies
• pluralization rules
• Add your own initializers as needed

The Rails Configuration Object

# Defined in railties/lib/initializer.rb
Rails.root
Rails.env
Rails.version
Rails.configuration.load_paths
Rails.configuration.gems
Rails.configuration.plugins
Rails.configuration.time_zone
Rails.configuration.i18n

Debugging

• raise @object.inspect
• raise User.instance_methods(false).sort.join(”, “)
• <%= debug @object %>
• script/console
• The error log (at log/development.log)