= CanCan
{}[http://badge.fury.io/rb/cancan]
{}[http://travis-ci.org/ryanb/cancan]
{}[https://codeclimate.com/github/ryanb/cancan]
Wiki[https://github.com/ryanb/cancan/wiki], RDocs[http://rdoc.info/projects/ryanb/cancan], Screencast[http://railscasts.com/episodes/192-authorization-with-cancan]
CanCan is an authorization library for Ruby on Rails which restricts what resources a given user is allowed to access. All permissions are defined in a single location (the +Ability+ class) and not duplicated across controllers, views, and database queries.
== Installation
In Rails 3, add this to your Gemfile and run the +bundle+ command.
gem "cancan"
In Rails 2, add this to your environment.rb file.
config.gem "cancan"
Alternatively, you can install it as a plugin.
rails plugin install git://github.com/ryanb/cancan.git
== Getting Started
CanCan expects a +current_user+ method to exist in the controller. First, set up some authentication (such as Authlogic[https://github.com/binarylogic/authlogic] or Devise[https://github.com/plataformatec/devise]). See {Changing Defaults}[https://github.com/ryanb/cancan/wiki/changing-defaults] if you need different behavior.
=== 1. Define Abilities
User permissions are defined in an +Ability+ class. CanCan 1.5 includes a Rails 3 generator for creating this class.
rails g cancan:ability
In Rails 2.3, just add a new class in app/models/ability.rb with the following contents:
class Ability
include CanCan::Ability
def initialize(user)
end
end
See {Defining Abilities}[https://github.com/ryanb/cancan/wiki/defining-abilities] for details.
=== 2. Check Abilities & Authorization
The current user's permissions can then be checked using the can? and cannot? methods in the view and controller.
<% if can? :update, @article %>
<%= link_to "Edit", edit_article_path(@article) %>
<% end %>
See {Checking Abilities}[https://github.com/ryanb/cancan/wiki/checking-abilities] for more information
The authorize! method in the controller will raise an exception if the user is not able to perform the given action.
def show
@article = Article.find(params[:id])
authorize! :read, @article
end
Setting this for every action can be tedious, therefore the +load_and_authorize_resource+ method is provided to automatically authorize all actions in a RESTful style resource controller. It will use a before filter to load the resource into an instance variable and authorize it for every action.
class ArticlesController < ApplicationController
load_and_authorize_resource
def show
# @article is already loaded and authorized
end
end
See {Authorizing Controller Actions}[https://github.com/ryanb/cancan/wiki/authorizing-controller-actions] for more information.
=== 3. Handle Unauthorized Access
If the user authorization fails, a CanCan::AccessDenied exception will be raised. You can catch this and modify its behavior in the +ApplicationController+.
class ApplicationController < ActionController::Base
rescue_from CanCan::AccessDenied do, exception, redirect_to root_url, :alert => exception.message
end
end
See {Exception Handling}[https://github.com/ryanb/cancan/wiki/exception-handling] for more information.
=== 4. Lock It Down
If you want to ensure authorization happens on every action in your application, add +check_authorization+ to your ApplicationController.
class ApplicationController < ActionController::Base
check_authorization
end
This will raise an exception if authorization is not performed in an action. If you want to skip this add +skip_authorization_check+ to a controller subclass. See {Ensure Authorization}[https://github.com/ryanb/cancan/wiki/Ensure-Authorization] for more information.
== Wiki Docs
- {Upgrading to 1.6}[https://github.com/ryanb/cancan/wiki/Upgrading-to-1.6]
- {Defining Abilities}[https://github.com/ryanb/cancan/wiki/Defining-Abilities]
- {Checking Abilities}[https://github.com/ryanb/cancan/wiki/Checking-Abilities]
- {Authorizing Controller Actions}[https://github.com/ryanb/cancan/wiki/Authorizing-Controller-Actions]
- {Exception Handling}[https://github.com/ryanb/cancan/wiki/Exception-Handling]
- {Changing Defaults}[https://github.com/ryanb/cancan/wiki/Changing-Defaults]
- {See more}[https://github.com/ryanb/cancan/wiki]
== Questions or Problems?
If you have any issues with CanCan which you cannot find the solution to in the documentation[https://github.com/ryanb/cancan/wiki], please add an {issue on GitHub}[https://github.com/ryanb/cancan/issues] or fork the project and send a pull request.
To get the specs running you should call +bundle+ and then +rake+. See the {spec/README}[https://github.com/ryanb/cancan/blob/master/spec/README.rdoc] for more information.
== Special Thanks
CanCan was inspired by declarative_authorization[https://github.com/stffn/declarative_authorization/] and aegis[https://github.com/makandra/aegis]. Also many thanks to the CanCan contributors[https://github.com/ryanb/cancan/contributors]. See the CHANGELOG[https://github.com/ryanb/cancan/blob/master/CHANGELOG.rdoc] for the full list.