CanCanCan System

Conventions & helpers simplifying the use of CanCanCan in complex Rails applications. CanCanCan System simplifies authorizing collaborations, memberships and more across a complex structure of models.

To describe complex abilities CanCanCan System relies on two different constructs: ActiveRecord objects, and relationships of users to those objects.

CanCanCan System uses two attributes on objects to describe abilities:

• ability: Describes the default ability of users without a special relationship with an object.
• visiblity: Specifies whether an object is visible to other users than the creator.

CanCanCan System uses one attribute on relationships to describe abilities:

• ability: Describes the ability of a user with the related object.

ability can have any CanCanCan permission, 'admin' (:manage), 'user' (:modify) or 'guest' (:read) as value while visiblity is limited to public and private.

• Installation
• Usage
  • Defining abilities
    • Public abilities
    • acts_as_belongable abilities
    • Membership abilities
  • Get abilities
• Testing
• To Do
• Contributing
  • Semantic versioning

CanCanCan System works with Rails 5 onwards. You can add it to your Gemfile with:

gem 'cancancan-system'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cancancan-system

If you always want to be up to date fetch the latest from GitHub in your Gemfile:

gem 'cancancan-system', github: 'jonhue/cancancan-system'

Now run the generator:

$ rails g cancancan_system

To wrap things up, migrate the changes to your database:

$ rails db:migrate

To get started add CanCanCan System to your Ability class (app/models/ability.rb) and add the required :modify alias:

class Ability
  include CanCan::Ability
  include CanCanCan::System::Ability

  def initialize(user)
    modify([:create, :read, :update, :destroy])
  end
end

Note: The aliases (:create, :read, :update, :destroy) can be custom.

You should add the ability attribute to ActiveRecord models you want to define abilities for:

add_column :users, :ability, :string, default: 'guest'

And you should add a visiblity attribute to ActiveRecord models you want to define public abilities for:

add_column :users, :visiblity, :string, default: 'public'

CanCanCan System makes an abilities method available which simplifies setting up common abilities:

def initialize(user)
  abilities(Post, user)
end

This is equivalent to:

def initialize(user)
  public_abilities(Post)
  can(:manage, Post, user_id: user.id) if user
end

You can also use the abilities method with custom column names and polymorphic associations. This comes in handy when using the NotificationsRails gem:

def initialize(user)
  abilities(Notification, user, column: 'target', polymorphic: true, public_abilities: false)
end

Note: Set column to nil or '' to use the id attribute.

This is equivalent to:

def initialize(user)
  can(:manage, Notification, target_id: user.id, target_type: user.class.name) if user
end

Learn more about the public_abilities method here.

The public_abilities method defines the object-abilities without a user being present:

def initialize(user)
  public_abilities(Post)
end

This is equivalent to:

def initialize(user)
  can(:manage, Post, ability: 'admin', visibility: 'public')
  can(:modify, Post, ability: 'user', visibility: 'public')
  can(:read, Post, ability: 'guest', visibility: 'public')
end

CanCanCan System integrates with the acts_as_belongable gem to make defining abilities for relationships dead simple.

Let's say our users can be a member of multiple organizations:

class User < ApplicationRecord
  acts_as_belongable
  belongable :member_of_organizations, 'Organization', scope: :membership
  has_many :organizations
end

class Organization < ApplicationRecord
  acts_as_belonger
  belonger :members, 'User', scope: :membership
  belongs_to :user
end

We would then just do:

def initialize(user)
  abilities(Organization, user) do
    belonger_abilities(Organization, user, scope: :membership)
  end
end

Note: This can be done in the same way with belongable_abilities for belongable relationships.

Now we are able to add members to our organizations and set their abilities:

Organization.first.add_belongable(User.first, scope: :membership, ability: 'admin')

Note: The scope option is optional. If omitted, the defined abilities will apply to all belongings regardless of their scope.

Now, let us assume that we have another model: Post.

class User < ApplicationRecord
  acts_as_belongable
  belongable :member_of_organizations, 'Organization', scope: :membership
  has_many :posts
  has_many :organizations
end

class Organization < ApplicationRecord
  acts_as_belonger
  belonger :members, 'User', scope: :membership
  has_many :posts
  belongs_to :user
end

class Post < ApplicationRecord
  belongs_to :user
  belongs_to :organization
end

You want the posts of an organization to be accessible for its members. It doesn't get any simpler than this:

def initialize(user)
  abilities(Post, user) do
    membership_abilities('Organization', Post, user, scope: :membership)
  end
end

Note: The scope option is optional. If omitted, the defined abilities will apply to all belongings regardless of their scope.

You are also able to perform some customization:

class Post < ApplicationRecord
  belongs_to :user
  belongs_to :object, polymorphic: true
end

def initialize(user)
  abilities(Post, user) do
    membership_abilities('Organization', Post, user, scope: :membership, column: 'object', polymorphic: true)
  end
end

Another option is to use the acts_as_belongable gem to associate posts with organizations:

class Organization < ApplicationRecord
  acts_as_belonger
  belonger :members, 'User', scope: :membership
  belonger :posts, 'Post'
  has_many :posts
  belongs_to :user
end

class Post < ApplicationRecord
  acts_as_belongable
  belongable :organizations, 'Organization'
  belongs_to :user
end

def initialize(user)
  abilities(Post, user) do
    organization_abilities(Post, user, scope: :membership, acts_as_belongable: true)
  end
end

Note: If your acts_as_belongable association in the Post model is not following the CanCanCan System naming convention, you can override it by passing the column option.

You can use the ability method to get the ability of an ActiveRecord object:

Organization.first.ability
# => 'guest'

ability(Organization.first)
# => :read

It returns a symbol or nil.

1. Fork this repository

2. Clone your forked git locally

3. Install dependencies

   $ bundle install

4. Run specs

   $ bundle exec rspec

5. Run RuboCop

   $ bundle exec rubocop

We use GitHub projects to coordinate the work on this project.

To propose your ideas, initiate the discussion by adding a new issue.

We hope that you will consider contributing to CanCanCan System. Please read this short overview for some information about how to get started:

Learn more about contributing to this repository, Code of Conduct

CanCanCan System follows Semantic Versioning 2.0 as defined at http://semver.org.