256 lines
10 KiB
Text
256 lines
10 KiB
Text
== Welcome to Rails
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Rails is a web-application framework that includes everything needed to create
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database-backed web applications according to the Model-View-Control pattern.
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This pattern splits the view (also called the presentation) into "dumb" templates
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that are primarily responsible for inserting pre-built data in between HTML tags.
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The model contains the "smart" domain objects (such as Account, Product, Person,
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Post) that holds all the business logic and knows how to persist themselves to
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a database. The controller handles the incoming requests (such as Save New Account,
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Update Product, Show Post) by manipulating the model and directing data to the view.
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In Rails, the model is handled by what's called an object-relational mapping
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layer entitled Active Record. This layer allows you to present the data from
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database rows as objects and embellish these data objects with business logic
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methods. You can read more about Active Record in
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link:files/vendor/rails/activerecord/README.html.
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The controller and view are handled by the Action Pack, which handles both
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layers by its two parts: Action View and Action Controller. These two layers
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are bundled in a single package due to their heavy interdependence. This is
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unlike the relationship between the Active Record and Action Pack that is much
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more separate. Each of these packages can be used independently outside of
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Rails. You can read more about Action Pack in
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link:files/vendor/rails/actionpack/README.html.
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== Getting Started
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1. At the command prompt, start a new Rails application using the <tt>rails</tt> command
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and your application name. Ex: rails myapp
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2. Change directory into myapp and start the web server: <tt>script/server</tt> (run with --help for options)
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3. Go to http://localhost:3000/ and get "Welcome aboard: You're riding the Rails!"
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4. Follow the guidelines to start developing your application
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== Web Servers
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By default, Rails will try to use Mongrel and lighttpd if they are installed, otherwise
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Rails will use WEBrick, the webserver that ships with Ruby. When you run script/server,
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Rails will check if Mongrel exists, then lighttpd and finally fall back to WEBrick. This ensures
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that you can always get up and running quickly.
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Mongrel is a Ruby-based webserver with a C component (which requires compilation) that is
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suitable for development and deployment of Rails applications. If you have Ruby Gems installed,
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getting up and running with mongrel is as easy as: <tt>gem install mongrel</tt>.
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More info at: http://mongrel.rubyforge.org
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If Mongrel is not installed, Rails will look for lighttpd. It's considerably faster than
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Mongrel and WEBrick and also suited for production use, but requires additional
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installation and currently only works well on OS X/Unix (Windows users are encouraged
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to start with Mongrel). We recommend version 1.4.11 and higher. You can download it from
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http://www.lighttpd.net.
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And finally, if neither Mongrel or lighttpd are installed, Rails will use the built-in Ruby
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web server, WEBrick. WEBrick is a small Ruby web server suitable for development, but not
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for production.
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But of course its also possible to run Rails on any platform that supports FCGI.
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Apache, LiteSpeed, IIS are just a few. For more information on FCGI,
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please visit: http://wiki.rubyonrails.com/rails/pages/FastCGI
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== Apache .htaccess example
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# General Apache options
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AddHandler fastcgi-script .fcgi
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AddHandler cgi-script .cgi
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Options +FollowSymLinks +ExecCGI
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# If you don't want Rails to look in certain directories,
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# use the following rewrite rules so that Apache won't rewrite certain requests
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#
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# Example:
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# RewriteCond %{REQUEST_URI} ^/notrails.*
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# RewriteRule .* - [L]
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# Redirect all requests not available on the filesystem to Rails
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# By default the cgi dispatcher is used which is very slow
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#
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# For better performance replace the dispatcher with the fastcgi one
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#
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# Example:
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# RewriteRule ^(.*)$ dispatch.fcgi [QSA,L]
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RewriteEngine On
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# If your Rails application is accessed via an Alias directive,
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# then you MUST also set the RewriteBase in this htaccess file.
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#
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# Example:
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# Alias /myrailsapp /path/to/myrailsapp/public
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# RewriteBase /myrailsapp
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RewriteRule ^$ index.html [QSA]
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RewriteRule ^([^.]+)$ $1.html [QSA]
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RewriteCond %{REQUEST_FILENAME} !-f
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RewriteRule ^(.*)$ dispatch.cgi [QSA,L]
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# In case Rails experiences terminal errors
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# Instead of displaying this message you can supply a file here which will be rendered instead
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#
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# Example:
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# ErrorDocument 500 /500.html
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ErrorDocument 500 "<h2>Application error</h2>Rails application failed to start properly"
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== Debugging Rails
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Sometimes your application goes wrong. Fortunately there are a lot of tools that
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will help you debug it and get it back on the rails.
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First area to check is the application log files. Have "tail -f" commands running
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on the server.log and development.log. Rails will automatically display debugging
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and runtime information to these files. Debugging info will also be shown in the
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browser on requests from 127.0.0.1.
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You can also log your own messages directly into the log file from your code using
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the Ruby logger class from inside your controllers. Example:
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class WeblogController < ActionController::Base
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def destroy
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@weblog = Weblog.find(params[:id])
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@weblog.destroy
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logger.info("#{Time.now} Destroyed Weblog ID ##{@weblog.id}!")
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end
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end
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The result will be a message in your log file along the lines of:
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Mon Oct 08 14:22:29 +1000 2007 Destroyed Weblog ID #1
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More information on how to use the logger is at http://www.ruby-doc.org/core/
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Also, Ruby documentation can be found at http://www.ruby-lang.org/ including:
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* The Learning Ruby (Pickaxe) Book: http://www.ruby-doc.org/docs/ProgrammingRuby/
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* Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
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These two online (and free) books will bring you up to speed on the Ruby language
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and also on programming in general.
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== Debugger
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Debugger support is available through the debugger command when you start your Mongrel or
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Webrick server with --debugger. This means that you can break out of execution at any point
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in the code, investigate and change the model, AND then resume execution!
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You need to install ruby-debug to run the server in debugging mode. With gems, use 'gem install ruby-debug'
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Example:
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class WeblogController < ActionController::Base
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def index
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@posts = Post.find(:all)
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debugger
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end
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end
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So the controller will accept the action, run the first line, then present you
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with a IRB prompt in the server window. Here you can do things like:
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>> @posts.inspect
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=> "[#<Post:0x14a6be8 @attributes={\"title\"=>nil, \"body\"=>nil, \"id\"=>\"1\"}>,
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#<Post:0x14a6620 @attributes={\"title\"=>\"Rails you know!\", \"body\"=>\"Only ten..\", \"id\"=>\"2\"}>]"
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>> @posts.first.title = "hello from a debugger"
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=> "hello from a debugger"
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...and even better is that you can examine how your runtime objects actually work:
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>> f = @posts.first
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=> #<Post:0x13630c4 @attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>
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>> f.
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Display all 152 possibilities? (y or n)
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Finally, when you're ready to resume execution, you enter "cont"
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== Console
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You can interact with the domain model by starting the console through <tt>script/console</tt>.
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Here you'll have all parts of the application configured, just like it is when the
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application is running. You can inspect domain models, change values, and save to the
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database. Starting the script without arguments will launch it in the development environment.
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Passing an argument will specify a different environment, like <tt>script/console production</tt>.
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To reload your controllers and models after launching the console run <tt>reload!</tt>
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== dbconsole
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You can go to the command line of your database directly through <tt>script/dbconsole</tt>.
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You would be connected to the database with the credentials defined in database.yml.
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Starting the script without arguments will connect you to the development database. Passing an
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argument will connect you to a different database, like <tt>script/dbconsole production</tt>.
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Currently works for mysql, postgresql and sqlite.
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== Description of Contents
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app
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Holds all the code that's specific to this particular application.
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app/controllers
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Holds controllers that should be named like weblogs_controller.rb for
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automated URL mapping. All controllers should descend from ApplicationController
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which itself descends from ActionController::Base.
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app/models
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Holds models that should be named like post.rb.
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Most models will descend from ActiveRecord::Base.
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app/views
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Holds the template files for the view that should be named like
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weblogs/index.html.erb for the WeblogsController#index action. All views use eRuby
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syntax.
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app/views/layouts
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Holds the template files for layouts to be used with views. This models the common
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header/footer method of wrapping views. In your views, define a layout using the
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<tt>layout :default</tt> and create a file named default.html.erb. Inside default.html.erb,
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call <% yield %> to render the view using this layout.
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app/helpers
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Holds view helpers that should be named like weblogs_helper.rb. These are generated
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for you automatically when using script/generate for controllers. Helpers can be used to
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wrap functionality for your views into methods.
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config
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Configuration files for the Rails environment, the routing map, the database, and other dependencies.
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db
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Contains the database schema in schema.rb. db/migrate contains all
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the sequence of Migrations for your schema.
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doc
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This directory is where your application documentation will be stored when generated
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using <tt>rake doc:app</tt>
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lib
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Application specific libraries. Basically, any kind of custom code that doesn't
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belong under controllers, models, or helpers. This directory is in the load path.
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public
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The directory available for the web server. Contains subdirectories for images, stylesheets,
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and javascripts. Also contains the dispatchers and the default HTML files. This should be
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set as the DOCUMENT_ROOT of your web server.
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script
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Helper scripts for automation and generation.
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test
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Unit and functional tests along with fixtures. When using the script/generate scripts, template
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test files will be generated for you and placed in this directory.
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vendor
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External libraries that the application depends on. Also includes the plugins subdirectory.
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If the app has frozen rails, those gems also go here, under vendor/rails/.
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This directory is in the load path.
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