262 lines
9.0 KiB
Plaintext
262 lines
9.0 KiB
Plaintext
== 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"
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templates that are primarily responsible for inserting pre-built data in between
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HTML tags. The model contains the "smart" domain objects (such as Account,
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Product, Person, Post) that holds all the business logic and knows how to
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persist themselves to a database. The controller handles the incoming requests
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(such as Save New Account, Update Product, Show Post) by manipulating the model
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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, create a new Rails application:
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<tt>rails new myapp</tt> (where <tt>myapp</tt> is the application name)
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2. Change directory to <tt>myapp</tt> and start the web server:
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<tt>cd myapp; rails server</tt> (run with --help for options)
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3. Go to http://localhost:3000/ and you'll see:
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"Welcome aboard: You're riding Ruby on Rails!"
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4. Follow the guidelines to start developing your application. You can find
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the following resources handy:
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* The Getting Started Guide: http://guides.rubyonrails.org/getting_started.html
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* Ruby on Rails Tutorial Book: http://www.railstutorial.org/
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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
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running on the server.log and development.log. Rails will automatically display
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debugging and runtime information to these files. Debugging info will also be
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shown in the 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
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using 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/. There are
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several books available online as well:
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* Programming Ruby: http://www.ruby-doc.org/docs/ProgrammingRuby/ (Pickaxe)
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* Learn to Program: http://pine.fm/LearnToProgram/ (a beginners guide)
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These two books will bring you up to speed on the Ruby language and also on
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programming in general.
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== Debugger
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Debugger support is available through the debugger command when you start your
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Mongrel or WEBrick server with --debugger. This means that you can break out of
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execution at any point in the code, investigate and change the model, and then,
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resume execution! You need to install ruby-debug to run the server in debugging
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mode. With gems, use <tt>sudo gem install ruby-debug</tt>. Example:
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class WeblogController < ActionController::Base
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def index
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@posts = Post.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
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@attributes={"title"=>nil, "body"=>nil, "id"=>"1"}>,
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#<Post:0x14a6620
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@attributes={"title"=>"Rails", "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, 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 can enter "cont".
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== Console
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The console is a Ruby shell, which allows you to interact with your
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application's domain model. Here you'll have all parts of the application
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configured, just like it is when the application is running. You can inspect
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domain models, change values, and save to the database. Starting the script
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without arguments will launch it in the development environment.
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To start the console, run <tt>rails console</tt> from the application
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directory.
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Options:
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* Passing the <tt>-s, --sandbox</tt> argument will rollback any modifications
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made to the database.
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* Passing an environment name as an argument will load the corresponding
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environment. Example: <tt>rails console production</tt>.
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To reload your controllers and models after launching the console run
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<tt>reload!</tt>
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More information about irb can be found at:
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link:http://www.rubycentral.org/pickaxe/irb.html
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== dbconsole
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You can go to the command line of your database directly through <tt>rails
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dbconsole</tt>. You would be connected to the database with the credentials
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defined in database.yml. Starting the script without arguments will connect you
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to the development database. Passing an argument will connect you to a different
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database, like <tt>rails dbconsole production</tt>. Currently works for MySQL,
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PostgreSQL and SQLite 3.
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== Description of Contents
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The default directory structure of a generated Ruby on Rails application:
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|-- app
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| |-- assets
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| | |-- images
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| | |-- javascripts
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| | `-- stylesheets
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| |-- controllers
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| |-- helpers
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| |-- mailers
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| |-- models
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| `-- views
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| `-- layouts
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|-- config
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| |-- environments
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| |-- initializers
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| `-- locales
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|-- db
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|-- doc
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|-- lib
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| |-- assets
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| `-- tasks
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|-- log
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|-- public
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|-- script
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|-- test
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| |-- fixtures
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| |-- functional
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| |-- integration
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| |-- performance
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| `-- unit
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|-- tmp
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| `-- cache
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| `-- assets
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`-- vendor
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|-- assets
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| |-- javascripts
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| `-- stylesheets
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`-- plugins
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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/assets
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Contains subdirectories for images, stylesheets, and JavaScript files.
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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
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ApplicationController 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. Models descend from
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ActiveRecord::Base by default.
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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
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eRuby syntax by default.
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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
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common header/footer method of wrapping views. In your views, define a layout
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using the <tt>layout :default</tt> and create a file named default.html.erb.
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Inside default.html.erb, call <% yield %> to render the view using this
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layout.
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app/helpers
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Holds view helpers that should be named like weblogs_helper.rb. These are
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generated for you automatically when using generators for controllers.
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Helpers can be used to 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,
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and other dependencies.
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db
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Contains the database schema in schema.rb. db/migrate contains all the
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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
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generated 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
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doesn't belong under controllers, models, or helpers. This directory is in
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the load path.
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public
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The directory available for the web server. Also contains the dispatchers and the
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default HTML files. This should be set as the DOCUMENT_ROOT of your web
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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 rails generate
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command, template test files will be generated for you and placed in this
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directory.
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vendor
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External libraries that the application depends on. Also includes the plugins
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subdirectory. If the app has frozen rails, those gems also go here, under
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vendor/rails/. This directory is in the load path.
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