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1 == Welcome to Rails
3 Rails is a web-application framework that includes everything needed to create
4 database-backed web applications according to the Model-View-Control pattern.
6 This pattern splits the view (also called the presentation) into "dumb" templates
7 that are primarily responsible for inserting pre-built data in between HTML tags.
8 The model contains the "smart" domain objects (such as Account, Product, Person,
9 Post) that holds all the business logic and knows how to persist themselves to
10 a database. The controller handles the incoming requests (such as Save New Account,
11 Update Product, Show Post) by manipulating the model and directing data to the view.
13 In Rails, the model is handled by what's called an object-relational mapping
14 layer entitled Active Record. This layer allows you to present the data from
15 database rows as objects and embellish these data objects with business logic
16 methods. You can read more about Active Record in
17 link:files/vendor/rails/activerecord/README.html.
19 The controller and view are handled by the Action Pack, which handles both
20 layers by its two parts: Action View and Action Controller. These two layers
21 are bundled in a single package due to their heavy interdependence. This is
22 unlike the relationship between the Active Record and Action Pack that is much
23 more separate. Each of these packages can be used independently outside of
24 Rails. You can read more about Action Pack in
25 link:files/vendor/rails/actionpack/README.html.
28 == Getting Started
30 1. At the command prompt, start a new Rails application using the <tt>rails</tt> command
31 and your application name. Ex: rails myapp
32 2. Change directory into myapp and start the web server: <tt>script/server</tt> (run with --help for options)
33 3. Go to http://localhost:3000/ and get "Welcome aboard: You're riding the Rails!"
34 4. Follow the guidelines to start developing your application
37 == Web Servers
39 By default, Rails will try to use Mongrel if it's are installed when started with script/server, otherwise Rails will use WEBrick, the webserver that ships with Ruby. But you can also use Rails
40 with a variety of other web servers.
42 Mongrel is a Ruby-based webserver with a C component (which requires compilation) that is
43 suitable for development and deployment of Rails applications. If you have Ruby Gems installed,
44 getting up and running with mongrel is as easy as: <tt>gem install mongrel</tt>.
45 More info at:
47 Say other Ruby web servers like Thin and Ebb or regular web servers like Apache or LiteSpeed or
48 Lighttpd or IIS. The Ruby web servers are run through Rack and the latter can either be setup to use
49 FCGI or proxy to a pack of Mongrels/Thin/Ebb servers.
51 == Apache .htaccess example for FCGI/CGI
53 # General Apache options
54 AddHandler fastcgi-script .fcgi
55 AddHandler cgi-script .cgi
56 Options +FollowSymLinks +ExecCGI
58 # If you don't want Rails to look in certain directories,
59 # use the following rewrite rules so that Apache won't rewrite certain requests
60 #
61 # Example:
62 # RewriteCond %{REQUEST_URI} ^/notrails.*
63 # RewriteRule .* - [L]
65 # Redirect all requests not available on the filesystem to Rails
66 # By default the cgi dispatcher is used which is very slow
67 #
68 # For better performance replace the dispatcher with the fastcgi one
69 #
70 # Example:
71 # RewriteRule ^(.*)$ dispatch.fcgi [QSA,L]
72 RewriteEngine On
74 # If your Rails application is accessed via an Alias directive,
75 # then you MUST also set the RewriteBase in this htaccess file.
76 #
77 # Example:
78 # Alias /myrailsapp /path/to/myrailsapp/public
79 # RewriteBase /myrailsapp
81 RewriteRule ^$ index.html [QSA]
82 RewriteRule ^([^.]+)$ $1.html [QSA]
83 RewriteCond %{REQUEST_FILENAME} !-f
84 RewriteRule ^(.*)$ dispatch.cgi [QSA,L]
86 # In case Rails experiences terminal errors
87 # Instead of displaying this message you can supply a file here which will be rendered instead
88 #
89 # Example:
90 # ErrorDocument 500 /500.html
92 ErrorDocument 500 "<h2>Application error</h2>Rails application failed to start properly"
95 == Debugging Rails
97 Sometimes your application goes wrong. Fortunately there are a lot of tools that
98 will help you debug it and get it back on the rails.
100 First area to check is the application log files. Have "tail -f" commands running
101 on the server.log and development.log. Rails will automatically display debugging
102 and runtime information to these files. Debugging info will also be shown in the
103 browser on requests from
105 You can also log your own messages directly into the log file from your code using
106 the Ruby logger class from inside your controllers. Example:
108 class WeblogController < ActionController::Base
109 def destroy
110 @weblog = Weblog.find(params[:id])
111 @weblog.destroy
112"#{} Destroyed Weblog ID ##{}!")
113 end
114 end
116 The result will be a message in your log file along the lines of:
118 Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1
120 More information on how to use the logger is at
122 Also, Ruby documentation can be found at including:
124 * The Learning Ruby (Pickaxe) Book:
125 * Learn to Program: (a beginners guide)
127 These two online (and free) books will bring you up to speed on the Ruby language
128 and also on programming in general.
131 == Debugger
133 Debugger support is available through the debugger command when you start your Mongrel or
134 Webrick server with --debugger. This means that you can break out of execution at any point
135 in the code, investigate and change the model, AND then resume execution!
136 You need to install ruby-debug to run the server in debugging mode. With gems, use 'gem install ruby-debug'
137 Example:
139 class WeblogController < ActionController::Base
140 def index
141 @posts = Post.find(:all)
142 debugger
143 end
144 end
146 So the controller will accept the action, run the first line, then present you
147 with a IRB prompt in the server window. Here you can do things like:
149 >> @posts.inspect
150 => "[#<Post:0x14a6be8 @attributes={\"title\"=>nil, \"body\"=>nil, \"id\"=>\"1\"}>,
151 #<Post:0x14a6620 @attributes={\"title\"=>\"Rails you know!\", \"body\"=>\"Only ten..\", \"id\"=>\"2\"}>]"
152 >> @posts.first.title = "hello from a debugger"
153 => "hello from a debugger"
155 ...and even better is that you can examine how your runtime objects actually work:
157 >> f = @posts.first
158 => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
159 >> f.
160 Display all 152 possibilities? (y or n)
162 Finally, when you're ready to resume execution, you enter "cont"
165 == Console
167 You can interact with the domain model by starting the console through <tt>script/console</tt>.
168 Here you'll have all parts of the application configured, just like it is when the
169 application is running. You can inspect domain models, change values, and save to the
170 database. Starting the script without arguments will launch it in the development environment.
171 Passing an argument will specify a different environment, like <tt>script/console production</tt>.
173 To reload your controllers and models after launching the console run <tt>reload!</tt>
175 == dbconsole
177 You can go to the command line of your database directly through <tt>script/dbconsole</tt>.
178 You would be connected to the database with the credentials defined in database.yml.
179 Starting the script without arguments will connect you to the development database. Passing an
180 argument will connect you to a different database, like <tt>script/dbconsole production</tt>.
181 Currently works for mysql, postgresql and sqlite.
183 == Description of Contents
185 app
186 Holds all the code that's specific to this particular application.
188 app/controllers
189 Holds controllers that should be named like weblogs_controller.rb for
190 automated URL mapping. All controllers should descend from ApplicationController
191 which itself descends from ActionController::Base.
193 app/models
194 Holds models that should be named like post.rb.
195 Most models will descend from ActiveRecord::Base.
197 app/views
198 Holds the template files for the view that should be named like
199 weblogs/index.html.erb for the WeblogsController#index action. All views use eRuby
200 syntax.
202 app/views/layouts
203 Holds the template files for layouts to be used with views. This models the common
204 header/footer method of wrapping views. In your views, define a layout using the
205 <tt>layout :default</tt> and create a file named default.html.erb. Inside default.html.erb,
206 call <% yield %> to render the view using this layout.
208 app/helpers
209 Holds view helpers that should be named like weblogs_helper.rb. These are generated
210 for you automatically when using script/generate for controllers. Helpers can be used to
211 wrap functionality for your views into methods.
213 config
214 Configuration files for the Rails environment, the routing map, the database, and other dependencies.
216 db
217 Contains the database schema in schema.rb. db/migrate contains all
218 the sequence of Migrations for your schema.
220 doc
221 This directory is where your application documentation will be stored when generated
222 using <tt>rake doc:app</tt>
224 lib
225 Application specific libraries. Basically, any kind of custom code that doesn't
226 belong under controllers, models, or helpers. This directory is in the load path.
228 public
229 The directory available for the web server. Contains subdirectories for images, stylesheets,
230 and javascripts. Also contains the dispatchers and the default HTML files. This should be
231 set as the DOCUMENT_ROOT of your web server.
233 script
234 Helper scripts for automation and generation.
236 test
237 Unit and functional tests along with fixtures. When using the script/generate scripts, template
238 test files will be generated for you and placed in this directory.
240 vendor
241 External libraries that the application depends on. Also includes the plugins subdirectory.
242 If the app has frozen rails, those gems also go here, under vendor/rails/.
243 This directory is in the load path.
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