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2008-04-20 initial commit
1 == Welcome to Rails
2
3 Rails is a web-application and persistence framework that includes everything
4 needed to create database-backed web-applications according to the
5 Model-View-Control pattern of separation. This pattern splits the view (also
6 called the presentation) into "dumb" templates that are primarily responsible
7 for inserting pre-built data in between HTML tags. The model contains the
8 "smart" domain objects (such as Account, Product, Person, Post) that holds all
9 the business logic and knows how to persist themselves to a database. The
10 controller handles the incoming requests (such as Save New Account, Update
11 Product, Show Post) by manipulating the model and directing data to the view.
12
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.
18
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.
26
27
28 == Getting Started
29
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 (If you've downloaded Rails in a complete tgz or zip, this step is already done)
33 2. Change directory into myapp and start the web server: <tt>script/server</tt> (run with --help for options)
34 3. Go to http://localhost:3000/ and get "Welcome aboard: You’re riding the Rails!"
35 4. Follow the guidelines to start developing your application
36
37
38 == Web Servers
39
40 By default, Rails will try to use Mongrel and lighttpd if they are installed, otherwise
41 Rails will use WEBrick, the webserver that ships with Ruby. When you run script/server,
42 Rails will check if Mongrel exists, then lighttpd and finally fall back to WEBrick. This ensures
43 that you can always get up and running quickly.
44
45 Mongrel is a Ruby-based webserver with a C component (which requires compilation) that is
46 suitable for development and deployment of Rails applications. If you have Ruby Gems installed,
47 getting up and running with mongrel is as easy as: <tt>gem install mongrel</tt>.
48 More info at: http://mongrel.rubyforge.org
49
50 If Mongrel is not installed, Rails will look for lighttpd. It's considerably faster than
51 Mongrel and WEBrick and also suited for production use, but requires additional
52 installation and currently only works well on OS X/Unix (Windows users are encouraged
53 to start with Mongrel). We recommend version 1.4.11 and higher. You can download it from
54 http://www.lighttpd.net.
55
56 And finally, if neither Mongrel or lighttpd are installed, Rails will use the built-in Ruby
57 web server, WEBrick. WEBrick is a small Ruby web server suitable for development, but not
58 for production.
59
60 But of course its also possible to run Rails on any platform that supports FCGI.
61 Apache, LiteSpeed, IIS are just a few. For more information on FCGI,
62 please visit: http://wiki.rubyonrails.com/rails/pages/FastCGI
63
64
65 == Debugging Rails
66
67 Sometimes your application goes wrong. Fortunately there are a lot of tools that
68 will help you debug it and get it back on the rails.
69
70 First area to check is the application log files. Have "tail -f" commands running
71 on the server.log and development.log. Rails will automatically display debugging
72 and runtime information to these files. Debugging info will also be shown in the
73 browser on requests from 127.0.0.1.
74
75 You can also log your own messages directly into the log file from your code using
76 the Ruby logger class from inside your controllers. Example:
77
78 class WeblogController < ActionController::Base
79 def destroy
80 @weblog = Weblog.find(params[:id])
81 @weblog.destroy
82 logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
83 end
84 end
85
86 The result will be a message in your log file along the lines of:
87
88 Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1
89
90 More information on how to use the logger is at http://www.ruby-doc.org/core/
91
92 Also, Ruby documentation can be found at http://www.ruby-lang.org/ including:
93
94 * The Learning Ruby (Pickaxe) Book: http://www.ruby-doc.org/docs/ProgrammingRuby/
95 * Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
96
97 These two online (and free) books will bring you up to speed on the Ruby language
98 and also on programming in general.
99
100
101 == Debugger
102
103 Debugger support is available through the debugger command when you start your Mongrel or
104 Webrick server with --debugger. This means that you can break out of execution at any point
105 in the code, investigate and change the model, AND then resume execution! Example:
106
107 class WeblogController < ActionController::Base
108 def index
109 @posts = Post.find(:all)
110 debugger
111 end
112 end
113
114 So the controller will accept the action, run the first line, then present you
115 with a IRB prompt in the server window. Here you can do things like:
116
117 >> @posts.inspect
118 => "[#<Post:0x14a6be8 @attributes={\"title\"=>nil, \"body\"=>nil, \"id\"=>\"1\"}>,
119 #<Post:0x14a6620 @attributes={\"title\"=>\"Rails you know!\", \"body\"=>\"Only ten..\", \"id\"=>\"2\"}>]"
120 >> @posts.first.title = "hello from a debugger"
121 => "hello from a debugger"
122
123 ...and even better is that you can examine how your runtime objects actually work:
124
125 >> f = @posts.first
126 => #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
127 >> f.
128 Display all 152 possibilities? (y or n)
129
130 Finally, when you're ready to resume execution, you enter "cont"
131
132
133 == Console
134
135 You can interact with the domain model by starting the console through <tt>script/console</tt>.
136 Here you'll have all parts of the application configured, just like it is when the
137 application is running. You can inspect domain models, change values, and save to the
138 database. Starting the script without arguments will launch it in the development environment.
139 Passing an argument will specify a different environment, like <tt>script/console production</tt>.
140
141 To reload your controllers and models after launching the console run <tt>reload!</tt>
142
143
144 == Description of Contents
145
146 app
147 Holds all the code that's specific to this particular application.
148
149 app/controllers
150 Holds controllers that should be named like weblogs_controller.rb for
151 automated URL mapping. All controllers should descend from ApplicationController
152 which itself descends from ActionController::Base.
153
154 app/models
155 Holds models that should be named like post.rb.
156 Most models will descend from ActiveRecord::Base.
157
158 app/views
159 Holds the template files for the view that should be named like
160 weblogs/index.erb for the WeblogsController#index action. All views use eRuby
161 syntax.
162
163 app/views/layouts
164 Holds the template files for layouts to be used with views. This models the common
165 header/footer method of wrapping views. In your views, define a layout using the
166 <tt>layout :default</tt> and create a file named default.erb. Inside default.erb,
167 call <% yield %> to render the view using this layout.
168
169 app/helpers
170 Holds view helpers that should be named like weblogs_helper.rb. These are generated
171 for you automatically when using script/generate for controllers. Helpers can be used to
172 wrap functionality for your views into methods.
173
174 config
175 Configuration files for the Rails environment, the routing map, the database, and other dependencies.
176
177 db
178 Contains the database schema in schema.rb. db/migrate contains all
179 the sequence of Migrations for your schema.
180
181 doc
182 This directory is where your application documentation will be stored when generated
183 using <tt>rake doc:app</tt>
184
185 lib
186 Application specific libraries. Basically, any kind of custom code that doesn't
187 belong under controllers, models, or helpers. This directory is in the load path.
188
189 public
190 The directory available for the web server. Contains subdirectories for images, stylesheets,
191 and javascripts. Also contains the dispatchers and the default HTML files. This should be
192 set as the DOCUMENT_ROOT of your web server.
193
194 script
195 Helper scripts for automation and generation.
196
197 test
198 Unit and functional tests along with fixtures. When using the script/generate scripts, template
199 test files will be generated for you and placed in this directory.
200
201 vendor
202 External libraries that the application depends on. Also includes the plugins subdirectory.
203 This directory is in the load path.
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