Rails 2.0.2 2.0.2

Welcome to Rails

Rails is a web-application and persistence framework that includes
everything needed to create database-backed web-applications according to
the Model-View-Control pattern of separation. This pattern splits the view
(also called the presentation) into “dumb” templates that are
primarily responsible for inserting pre-built data in between HTML tags.
The model contains the “smart” domain objects (such as Account,
Product, Person, Post) that holds all the business logic and knows how to
persist themselves to a database. The controller handles the incoming
requests (such as Save New Account, Update Product, Show Post) by
manipulating the model and directing data to the view.

In Rails, the model is handled by what’s called an object-relational
mapping layer entitled Active Record. This layer allows you to present the
data from database rows as objects and embellish these data objects with
business logic methods. You can read more about Active Record in link:files/vendor/rails/activerecord/README.html.

The controller and view are handled by the Action Pack, which handles both
layers by its two parts: Action View and Action Controller. These two
layers are bundled in a single package due to their heavy interdependence.
This is unlike the relationship between the Active Record and Action Pack
that is much more separate. Each of these packages can be used
independently outside of Rails. You can read more about Action Pack in link:files/vendor/rails/actionpack/README.html.

Getting Started

  1. At the command prompt, start a new Rails application using the
    rails command and your application name. Ex: rails myapp (If
    you’ve downloaded Rails in a complete tgz or zip, this step is
    already done)

  2. Change directory into myapp and start the web server:
    script/server (run with —help for options)

  3. Go to localhost:3000/ and get
    “Welcome aboard: You’re riding the Rails!”

  4. Follow the guidelines to start developing your application

Web Servers

By default, Rails will try to use Mongrel and lighttpd if they are
installed, otherwise Rails will use WEBrick, the webserver that ships with
Ruby. When you run script/server, Rails will check if Mongrel exists, then
lighttpd and finally fall back to WEBrick. This ensures that you can always
get up and running quickly.

Mongrel is a Ruby-based webserver with a C component (which requires
compilation) that is suitable for development and deployment of Rails
applications. If you have Ruby Gems installed, getting up and running with
mongrel is as easy as: gem install mongrel. More info at: mongrel.rubyforge.org

If Mongrel is not installed, Rails will look for lighttpd. It’s
considerably faster than Mongrel and WEBrick and also suited for production
use, but requires additional installation and currently only works well on
OS X/Unix (Windows users are encouraged to start with Mongrel). We
recommend version 1.4.11 and higher. You can download it from www.lighttpd.net.

And finally, if neither Mongrel or lighttpd are installed, Rails will use
the built-in Ruby web server, WEBrick. WEBrick is a small Ruby web server
suitable for development, but not for production.

But of course its also possible to run Rails on any platform that supports
FCGI. Apache, LiteSpeed, IIS are just a few. For more information on FCGI,
please visit: wiki.rubyonrails.com/rails/pages/FastCGI

Debugging Rails

Sometimes your application goes wrong. Fortunately there are a lot of tools
that will help you debug it and get it back on the rails.

First area to check is the application log files. Have “tail -f”
commands running on the server.log and development.log. Rails will
automatically display debugging and runtime information to these files.
Debugging info will also be shown in the browser on requests from

You can also log your own messages directly into the log file from your
code using the Ruby logger class from inside your controllers. Example:

class WeblogController < ActionController::Base
  def destroy
    @weblog = Weblog.find(params[:id])
    logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")

The result will be a message in your log file along the lines of:

Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1

More information on how to use the logger is at www.ruby-doc.org/core/

Also, Ruby documentation can be found at www.ruby-lang.org/ including:

These two online (and free) books will bring you up to speed on the Ruby
language and also on programming in general.


Debugger support is available through the debugger command when you start
your Mongrel or Webrick server with —debugger. This means that you
can break out of execution at any point in the code, investigate and change
the model, AND then resume execution! Example:

class WeblogController < ActionController::Base
  def index
    @posts = Post.find(:all)

So the controller will accept the action, run the first line, then present
you with a IRB prompt in the server window. Here you can do things like:

>> @posts.inspect
=> "[#<Post:0x14a6be8 @attributes={\"title\"=>nil, \"body\"=>nil, \"id\"=>\"1\"}>,
     #<Post:0x14a6620 @attributes={\"title\"=>\"Rails you know!\", \"body\"=>\"Only ten..\", \"id\"=>\"2\"}>]"
>> @posts.first.title = "hello from a debugger"
=> "hello from a debugger"

…and even better is that you can examine how your runtime objects
actually work:

>> f = @posts.first
=> #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
>> f.
Display all 152 possibilities? (y or n)

Finally, when you’re ready to resume execution, you enter


You can interact with the domain model by starting the console through
script/console. Here you’ll have all parts of the
application configured, just like it is when the application is running.
You can inspect domain models, change values, and save to the database.
Starting the script without arguments will launch it in the development
environment. Passing an argument will specify a different environment, like
script/console production.

To reload your controllers and models after launching the console run

Description of Contents


Holds all the code that's specific to this particular application.


Holds controllers that should be named like weblogs_controller.rb for
automated URL mapping. All controllers should descend from ApplicationController
which itself descends from ActionController::Base.


Holds models that should be named like post.rb.
Most models will descend from ActiveRecord::Base.


Holds the template files for the view that should be named like
weblogs/index.erb for the WeblogsController#index action. All views use eRuby


Holds the template files for layouts to be used with views. This models the common
header/footer method of wrapping views. In your views, define a layout using the
<tt>layout :default</tt> and create a file named default.erb. Inside default.erb,
call <% yield %> to render the view using this layout.


Holds view helpers that should be named like weblogs_helper.rb. These are generated
for you automatically when using script/generate for controllers. Helpers can be used to
wrap functionality for your views into methods.


Configuration files for the Rails environment, the routing map, the database, and other dependencies.


Contains the database schema in schema.rb.  db/migrate contains all
the sequence of Migrations for your schema.


This directory is where your application documentation will be stored when generated
using <tt>rake doc:app</tt>


Application specific libraries. Basically, any kind of custom code that doesn't
belong under controllers, models, or helpers. This directory is in the load path.


The directory available for the web server. Contains subdirectories for images, stylesheets,
and javascripts. Also contains the dispatchers and the default HTML files. This should be
set as the DOCUMENT_ROOT of your web server.


Helper scripts for automation and generation.


Unit and functional tests along with fixtures. When using the script/generate scripts, template
test files will be generated for you and placed in this directory.


External libraries that the application depends on. Also includes the plugins subdirectory.
This directory is in the load path.

Rails A class for creating random secret keys. This class will do its best to
create a random secret key that’s as secure as possible, using
whatever methods are available on the current platform. For example:

DispatchServlet A custom dispatch servlet for use with WEBrick. It dispatches requests
(using the Rails Dispatcher) to the appropriate controller/action. By
default, it restricts WEBrick to a managing a single Rails request at a
time, but you can change this behavior by setting
ActionController::Base.allow_concurrency to true.