== Welcome to Rails
Rails is a web-application framework that includes everything needed to create
database-backed web applications according to the Model-View-Control pattern.
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 <tt>rails</tt> command
and your application name. Ex: <tt>rails myapp</tt>
2. Change directory into myapp and start the web server: <tt>rails server</tt> (run with --help for options)
3. Go to http://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 if it's installed when started with <tt>rails server</tt>, otherwise
Rails will use WEBrick, the webserver that ships with Ruby. But you can also use Rails with a variety of
other web servers.
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: <tt>gem install mongrel</tt>.
More info at: http://mongrel.rubyforge.org
Other ruby web servers exist which can run your rails application, however <tt>rails server</tt> does
not search for them or start them. These include {Thin}[http://code.macournoyer.com/thin/], {Ebb}[http://ebb.rubyforge.org/], and Apache with {mod_rails}[http://www.modrails.com/].
For production use, often a web/proxy server such as {Apache}[http://apache.org], {Nginx}[http://nginx.net/], {LiteSpeed}[http://litespeedtech.com/], {Lighttpd}[http://www.lighttpd.net/] or {IIS}[http://www.iis.net/] is
deployed as the front-end server, with the chosen ruby web server running in the back-end
and receiving the proxied requests via one of several protocols (HTTP, CGI, FCGI).
== Apache .htaccess example for FCGI/CGI
General Apache options
AddHandler fastcgi-script .fcgi
AddHandler cgi-script .cgi
Options +FollowSymLinks +ExecCGI
If you don't want Rails to look in certain directories, use the following
rewrite rules so that Apache won't rewrite certain requests.
RewriteCond %{REQUEST_URI} ^/notrails.*
RewriteRule .* - [L]
Redirect all requests not available on the filesystem to Rails. By default the
cgi dispatcher is used which is very slow, for better performance replace the
dispatcher with the fastcgi one.
RewriteRule ^(.*)$ dispatch.fcgi [QSA,L]
RewriteEngine On
If your Rails application is accessed via an Alias directive, then you MUST also
set the RewriteBase in this htaccess file.
Alias /myrailsapp /path/to/myrailsapp/public
RewriteBase /myrailsapp
RewriteRule ^$ index.html [QSA]
RewriteRule ^([^.]+)$ $1.html [QSA]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ dispatch.cgi [QSA,L]
Incase Rails experiences terminal errors instead of displaying those messages you
can supply a file here which will be rendered instead.
ErrorDocument 500 /500.html
ErrorDocument 500 "<h2>Application error</h2>Rails application failed to start properly"
== 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 127.0.0.1.
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])
@weblog.destroy
logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
end
end
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 http://www.ruby-doc.org/core/
Also, Ruby documentation can be found at http://www.ruby-lang.org/ including:
* The Learning Ruby (Pickaxe) Book: http://www.ruby-doc.org/docs/ProgrammingRuby/
* Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
These two online (and free) books will bring you up to speed on the Ruby language
and also on programming in general.
== Debugger
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!
You need to install ruby-debug to run the server in debugging mode. With gems, use 'gem install ruby-debug'
Example:
class WeblogController < ActionController::Base
def index
@posts = Post.find(:all)
debugger
end
end
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 "cont"
== Console
The console is a ruby shell, which allows you to interact with your application's domain
model. 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.
To start the console, just run <tt>rails console</tt> from the application directory.
Options:
* Passing the <tt>-s, --sandbox</tt> argument will rollback any modifications made to the database.
* Passing an environment name as an argument will load the corresponding environment.
Example: <tt>rails console production</tt>.
More information about irb can be found at link:http://www.rubycentral.com/pickaxe/irb.html
== dbconsole
You can go to the command line of your database directly through <tt>rails dbconsole</tt>.
You would be connected to the database with the credentials defined in database.yml.
Starting the script without arguments will connect you to the development database. Passing an
argument will connect you to a different database, like <tt>rails dbconsole production</tt>.
Currently works for mysql, postgresql and sqlite.
== Description of Contents
The default directory structure of a generated Ruby on Rails applicartion:
|-- app
| |-- controllers
| |-- helpers
| |-- models
| `-- views
| `-- layouts
|-- config
| |-- environments
| |-- initializers
| `-- locales
|-- db
|-- doc
|-- lib
| `-- tasks
|-- log
|-- public
| |-- images
| |-- javascripts
| `-- stylesheets
|-- script
| `-- performance
|-- test
| |-- fixtures
| |-- functional
| |-- integration
| |-- performance
| `-- unit
|-- tmp
| |-- cache
| |-- pids
| |-- sessions
| `-- sockets
`-- vendor
`-- plugins
app
Holds all the code that's specific to this particular application.
app/controllers
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.
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
weblogs/index.html.erb for the WeblogsController#index action. All views use eRuby
syntax.
app/views/layouts
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.html.erb. Inside default.html.erb,
call <% yield %> to render the view using this layout.
app/helpers
Holds view helpers that should be named like weblogs_helper.rb. These are generated
for you automatically when using <tt>rails generate</tt> for controllers. Helpers can be used to
wrap functionality for your views into methods.
config
Configuration files for the Rails environment, the routing map, the database, and other dependencies.
db
Contains the database schema in schema.rb. db/migrate contains all
the sequence of Migrations for your schema.
doc
This directory is where your application documentation will be stored when generated
using <tt>rake doc:app</tt>
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. This should be
set as the DOCUMENT_ROOT of your web server.
script
Helper scripts for automation and generation.
test
Unit and functional tests along with fixtures. When using the <tt>rails generate</tt> scripts, template
test files will be generated for you and placed in this directory.
vendor
External libraries that the application depends on. Also includes the plugins subdirectory.
If the app has frozen rails, those gems also go here, under vendor/rails/.
This directory is in the load path.
d56e8be22d