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 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 files/vendor/rails/actionpack/README.html.

Getting started

  1. Run the WEBrick servlet: ruby script/server (run with –help for options) …or if you have lighttpd installed: ruby script/lighttpd (it's faster)

  2. Go to localhost:3000/ and get “Congratulations, you've put Ruby on Rails!”

  3. Follow the guidelines on the “Congratulations, you've put Ruby on Rails!” screen

Example for Apache conf

<VirtualHost *:80>
  ServerName rails
  DocumentRoot /path/application/public/
  ErrorLog /path/application/log/server.log

  <Directory /path/application/public/>
    Options ExecCGI FollowSymLinks
    AllowOverride all
    Allow from all
    Order allow,deny
  </Directory>
</VirtualHost>

NOTE: Be sure that CGIs can be executed in that directory as well. So ExecCGI should be on and “.cgi” should respond. All requests from 127.0.0.1 go through CGI, so no Apache restart is necessary for changes. All other requests go through FCGI (or mod_ruby), which requires a restart to show changes.

Debugging Rails

Have “tail -f” commands running on both the server.log, production.log, and test.log files. Rails will automatically display debugging and runtime information to these files. Debugging info will also be shown in the browser on requests from 127.0.0.1.

Breakpoints

Breakpoint support is available through the script/breakpointer client. 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
    breakpoint "Breaking out from the list"
  end
end

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

Executing breakpoint “Breaking out from the list” at …/webrick_server.rb:16 in 'breakpoint'

>> @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 breakpoint"
=> "hello from a breakpoint"

…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 press CTRL-D

Console

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 console production.

Description of contents

app

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

app/controllers

Holds controllers that should be named like weblog_controller.rb for
automated URL mapping. All controllers should descend from
ActionController::Base.

app/models

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

app/views

Holds the template files for the view that should be named like
weblog/index.rhtml for the WeblogController#index action. All views use eRuby
syntax. This directory can also be used to keep stylesheets, images, and so on
that can be symlinked to public.

app/helpers

Holds view helpers that should be named like weblog_helper.rb.

config

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

components

Self-contained mini-applications that can bundle together controllers, models, and views.

lib

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.

public

The directory available for the web server. Contains subdirectories for images, stylesheets,
and javascripts. Also contains the dispatchers and the default HTML files.

script

Helper scripts for automation and generation.

test

Unit and functional tests along with fixtures.

vendor

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