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author Edho Arief <edho@myconan.net>
date Sun, 26 Aug 2012 10:58:26 -0700
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1 == Welcome to Rails
2
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.
5
6 This pattern splits the view (also called the presentation) into "dumb"
7 templates that are primarily responsible for inserting pre-built data in between
8 HTML tags. The model contains the "smart" domain objects (such as Account,
9 Product, Person, Post) that holds all the business logic and knows how to
10 persist themselves to a database. The controller handles the incoming requests
11 (such as Save New Account, Update Product, Show Post) by manipulating the model
12 and directing data to the view.
13
14 In Rails, the model is handled by what's called an object-relational mapping
15 layer entitled Active Record. This layer allows you to present the data from
16 database rows as objects and embellish these data objects with business logic
17 methods. You can read more about Active Record in
18 link:files/vendor/rails/activerecord/README.html.
19
20 The controller and view are handled by the Action Pack, which handles both
21 layers by its two parts: Action View and Action Controller. These two layers
22 are bundled in a single package due to their heavy interdependence. This is
23 unlike the relationship between the Active Record and Action Pack that is much
24 more separate. Each of these packages can be used independently outside of
25 Rails. You can read more about Action Pack in
26 link:files/vendor/rails/actionpack/README.html.
27
28
29 == Getting Started
30
31 1. At the command prompt, create a new Rails application:
32 <tt>rails new myapp</tt> (where <tt>myapp</tt> is the application name)
33
34 2. Change directory to <tt>myapp</tt> and start the web server:
35 <tt>cd myapp; rails server</tt> (run with --help for options)
36
37 3. Go to http://localhost:3000/ and you'll see:
38 "Welcome aboard: You're riding Ruby on Rails!"
39
40 4. Follow the guidelines to start developing your application. You can find
41 the following resources handy:
42
43 * The Getting Started Guide: http://guides.rubyonrails.org/getting_started.html
44 * Ruby on Rails Tutorial Book: http://www.railstutorial.org/
45
46
47 == Debugging Rails
48
49 Sometimes your application goes wrong. Fortunately there are a lot of tools that
50 will help you debug it and get it back on the rails.
51
52 First area to check is the application log files. Have "tail -f" commands
53 running on the server.log and development.log. Rails will automatically display
54 debugging and runtime information to these files. Debugging info will also be
55 shown in the browser on requests from 127.0.0.1.
56
57 You can also log your own messages directly into the log file from your code
58 using the Ruby logger class from inside your controllers. Example:
59
60 class WeblogController < ActionController::Base
61 def destroy
62 @weblog = Weblog.find(params[:id])
63 @weblog.destroy
64 logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
65 end
66 end
67
68 The result will be a message in your log file along the lines of:
69
70 Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1!
71
72 More information on how to use the logger is at http://www.ruby-doc.org/core/
73
74 Also, Ruby documentation can be found at http://www.ruby-lang.org/. There are
75 several books available online as well:
76
77 * Programming Ruby: http://www.ruby-doc.org/docs/ProgrammingRuby/ (Pickaxe)
78 * Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
79
80 These two books will bring you up to speed on the Ruby language and also on
81 programming in general.
82
83
84 == Debugger
85
86 Debugger support is available through the debugger command when you start your
87 Mongrel or WEBrick server with --debugger. This means that you can break out of
88 execution at any point in the code, investigate and change the model, and then,
89 resume execution! You need to install ruby-debug to run the server in debugging
90 mode. With gems, use <tt>sudo gem install ruby-debug</tt>. Example:
91
92 class WeblogController < ActionController::Base
93 def index
94 @posts = Post.all
95 debugger
96 end
97 end
98
99 So the controller will accept the action, run the first line, then present you
100 with a IRB prompt in the server window. Here you can do things like:
101
102 >> @posts.inspect
103 => "[#<Post:0x14a6be8
104 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>,
105 #<Post:0x14a6620
106 @attributes={"title"=>"Rails", "body"=>"Only ten..", "id"=>"2"}>]"
107 >> @posts.first.title = "hello from a debugger"
108 => "hello from a debugger"
109
110 ...and even better, you can examine how your runtime objects actually work:
111
112 >> f = @posts.first
113 => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
114 >> f.
115 Display all 152 possibilities? (y or n)
116
117 Finally, when you're ready to resume execution, you can enter "cont".
118
119
120 == Console
121
122 The console is a Ruby shell, which allows you to interact with your
123 application's domain model. Here you'll have all parts of the application
124 configured, just like it is when the application is running. You can inspect
125 domain models, change values, and save to the database. Starting the script
126 without arguments will launch it in the development environment.
127
128 To start the console, run <tt>rails console</tt> from the application
129 directory.
130
131 Options:
132
133 * Passing the <tt>-s, --sandbox</tt> argument will rollback any modifications
134 made to the database.
135 * Passing an environment name as an argument will load the corresponding
136 environment. Example: <tt>rails console production</tt>.
137
138 To reload your controllers and models after launching the console run
139 <tt>reload!</tt>
140
141 More information about irb can be found at:
142 link:http://www.rubycentral.org/pickaxe/irb.html
143
144
145 == dbconsole
146
147 You can go to the command line of your database directly through <tt>rails
148 dbconsole</tt>. You would be connected to the database with the credentials
149 defined in database.yml. Starting the script without arguments will connect you
150 to the development database. Passing an argument will connect you to a different
151 database, like <tt>rails dbconsole production</tt>. Currently works for MySQL,
152 PostgreSQL and SQLite 3.
153
154 == Description of Contents
155
156 The default directory structure of a generated Ruby on Rails application:
157
158 |-- app
159 | |-- assets
160 | |-- images
161 | |-- javascripts
162 | `-- stylesheets
163 | |-- controllers
164 | |-- helpers
165 | |-- mailers
166 | |-- models
167 | `-- views
168 | `-- layouts
169 |-- config
170 | |-- environments
171 | |-- initializers
172 | `-- locales
173 |-- db
174 |-- doc
175 |-- lib
176 | `-- tasks
177 |-- log
178 |-- public
179 |-- script
180 |-- test
181 | |-- fixtures
182 | |-- functional
183 | |-- integration
184 | |-- performance
185 | `-- unit
186 |-- tmp
187 | |-- cache
188 | |-- pids
189 | |-- sessions
190 | `-- sockets
191 `-- vendor
192 |-- assets
193 `-- stylesheets
194 `-- plugins
195
196 app
197 Holds all the code that's specific to this particular application.
198
199 app/assets
200 Contains subdirectories for images, stylesheets, and JavaScript files.
201
202 app/controllers
203 Holds controllers that should be named like weblogs_controller.rb for
204 automated URL mapping. All controllers should descend from
205 ApplicationController which itself descends from ActionController::Base.
206
207 app/models
208 Holds models that should be named like post.rb. Models descend from
209 ActiveRecord::Base by default.
210
211 app/views
212 Holds the template files for the view that should be named like
213 weblogs/index.html.erb for the WeblogsController#index action. All views use
214 eRuby syntax by default.
215
216 app/views/layouts
217 Holds the template files for layouts to be used with views. This models the
218 common header/footer method of wrapping views. In your views, define a layout
219 using the <tt>layout :default</tt> and create a file named default.html.erb.
220 Inside default.html.erb, call <% yield %> to render the view using this
221 layout.
222
223 app/helpers
224 Holds view helpers that should be named like weblogs_helper.rb. These are
225 generated for you automatically when using generators for controllers.
226 Helpers can be used to wrap functionality for your views into methods.
227
228 config
229 Configuration files for the Rails environment, the routing map, the database,
230 and other dependencies.
231
232 db
233 Contains the database schema in schema.rb. db/migrate contains all the
234 sequence of Migrations for your schema.
235
236 doc
237 This directory is where your application documentation will be stored when
238 generated using <tt>rake doc:app</tt>
239
240 lib
241 Application specific libraries. Basically, any kind of custom code that
242 doesn't belong under controllers, models, or helpers. This directory is in
243 the load path.
244
245 public
246 The directory available for the web server. Also contains the dispatchers and the
247 default HTML files. This should be set as the DOCUMENT_ROOT of your web
248 server.
249
250 script
251 Helper scripts for automation and generation.
252
253 test
254 Unit and functional tests along with fixtures. When using the rails generate
255 command, template test files will be generated for you and placed in this
256 directory.
257
258 vendor
259 External libraries that the application depends on. Also includes the plugins
260 subdirectory. If the app has frozen rails, those gems also go here, under
261 vendor/rails/. This directory is in the load path.