Canard brings CanCan and RoleModel together to make role-based authorization in Rails easy. Your ability definitions gain their own folder and a little structure. The easiest way to get started is with the Canard generator. Canard progressively enhances the abilities of the model by applying role abilities on top of the model's base abilities. A User model with :admin and :manager roles would be defined:
class User < ActiveRecord::Base
acts_as_user :roles => [ :manager, :admin ]
end
If a User has both the :manager and :admin roles, Canard looks first for user abilities. Then it will look for other roles in the order that they are defined:
app/abilities/users.rb
app/abilities/manager.rb
app/abilities/admin.rb
Therefore each of the later abilities can build on its predecessor.
To generate some abilities for the User:
$ rails g canard:ability user can:[read,create]:[account,statement] cannot:destroy:account
create app/abilities/users.rb
invoke rspec
create spec/abilities/user_spec.rb
This action generates an ability folder in Rails root and an associated spec:
app.abilities/
users.rb
spec/abilities/
users_spec.rb
The resulting app/abilities/users.rb will look something like this:
Canard::Abilities.for(:user) do
can [:read, :create], Account
cannot [:destroy], Account
can [:read, :create], Statement
end
And its associated test spec/abilities/users_spec.rb will look something like this:
require_relative '../spec_helper'
require "cancan/matchers"
describe Ability, "for :user" do
before do
@user = Factory.create(:user_user)
end
subject { Ability.new(@user) }
describe 'on Account' do
before do
@account = Factory.create(:account)
end
it { should be_able_to( :read, @account ) }
it { should be_able_to( :create, @account ) }
it { should_not be_able_to( :destroy, @account ) }
end
# on Account
describe 'on Statement' do
before do
@statement = Factory.create(:statement)
end
it { should be_able_to( :read, @statement ) }
it { should be_able_to( :create, @statement ) }
end
# on Statement
end
You can also re-use abilities defined for one role in another. This allows you to 'inherit' abilities without having to assign all of the roles to the user. To do this, pass a list of role names to the includes_abilities_of method:
Canard::Abilities.for(:writer) do
can [:create], Post
can [:read], Post, user_id: user.id
end
Canard::Abilities.for(:reviewer) do
can [:read, :update], Post
end
Canard::Abilities.for(:admin) do
includes_abilities_of :writer, :reviewer
can [:delete], Post
end
A user assigned the :admin role will have all of the abilities of the :writer and :reviewer, along with their own abilities, without having to have those individual roles assigned to them.
Now let's generate some abilities for the manager and admin:
$ rails g canard:ability admin can:manage:[account,statement]
$ rails g canard:ability manager can:edit:statement
This generates two new sets of abilities in the abilities folder. Canard will apply these abilities by first loading the ability for the User model and then applying the abilities for each of the current user's roles.
If there is no user (i.e. logged out), Canard creates a guest and looks for a guest ability to apply:
$ rails g canard:ability guest can:create:user
This would generate a signup ability for a user who was not logged in.
Obviously the generators are just a starting point and should be used only to get you going. I strongly suggest that you add each new model to the abilities because the specs are easy to write and CanCan definitions are very clear and simple.
The :acts_as_user method will automatically define some named scopes for each role. For the User model above it will define the following scopes:
| Scope | Returns |
|---|---|
User.admins |
all the users with the admin role |
User.non_admins |
all the users without the admin role |
User.managers |
all the users with the manager role |
User.non_managers |
all the users without the manager role |
In addition to the role specific scopes it also adds some general scopes:
| Scope | Returns |
|---|---|
User.with_any_role(roles) |
all the users with any of the specified roles |
User.with_all_roles(roles) |
only the users with all the specified roles |
Add the canard gem to your Gemfile:
gem "canard"
Add the roles_mask field to your user table:
rails g migration add_roles_mask_to_users roles_mask:integer
rake db:migrate
That's it!
Sorry, you are out of luck. Canard has only been written and tested with Rails 3 and above.
Canard is ORM agnostic. ActiveRecord and Mongoid (thanks David Butler) adapters are currently implemented. New adapters can easily be added, but you'd need to check to see if CanCan can also support your adapter.
Canard stands on the shoulders of Ryan Bates' CanCan and Martin Rehfeld's RoleModel. You can read more about defining abilities on the CanCan wiki (https://github.com/ryanb/cancan/wiki). Canard implements the Ability class for you so you don't need the boilerplate code from Ryan's example:
class Ability
include CanCan::Ability
def initialize(user)
user ||= User.new # guest user (not logged in)
if user.admin?
can :manage, :all
else
can :read, :all
end
end
end
The Canard equivalent for non-admins would be:
Canard::Abilities.for(:user) do
can :read, :all
end
And for admins:
Canard::Abilities.for(:admin) do
can :manage, :all
end
Under the covers Canard uses RoleModel (https://github.com/martinrehfeld/role_model) to define roles. RoleModel is based on Ryan Bates' suggested approach to role based authorization which is documented in the CanCan wiki (https://github.com/ryanb/cancan/wiki/role-based-authorization).
- Fork the project.
- Make your feature addition or bug fix.
- Add tests for it (when I have some). This is important so I don't break it in a future version unintentionally.
- Commit. Do not mess with rakefile, version, or history. (If you want to have your own version, that is fine but bump version in a commit by itself so I can ignore it when I pull.)
- Send me a pull request. Bonus points for topic branches.
git log | grep Author | sort | uniq
- Alessandro Dal Grande
- David Butler
- Dmitriy Molodtsov
- Dmytro Salko
- James McCarthy
- Jesse McGinnis
- Joey Geiger
- Jon Kinney
- Justin Buchanan
- Morton Jonuschat
- Piotr Kuczynski
- Thomas Hoen
- Travis Berry
If you feel like contributing there is a TODO list in the root with a few ideas and opportunities!
Thanks to Ryan Bates for creating the awesome CanCan (http://wiki.github.com/ryanb/cancan) and Martin Rehfeld for implementing Role Based Authorization in the form of RoleModel (http://github.com/martinrehfeld/role_model).
Copyright (c) 2011-2017 James McCarthy, released under the MIT license
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