guise

An alternative to storing role resources in the database.

guise delegates type information to roles table that determines what a resource can be instantiated as. In essence, it's similar to single table inheritance, but with multiple inheritances possible.

Installation

Add this line to your application's Gemfile:

gem 'guise'

And then execute:

$ bundle

Or install it yourself as:

$ gem install guise

Usage

Create a table to store your type information:

rails generate model guises user:references title:string
rake db:migrate

Then add call the has_guises method in your model. This will setup the has_many association for you.

class User < ActiveRecord::Base
  has_guises :DeskWorker, :MailFowarder
end

This adds the following methods to the User class:

• :desk_workers and :mail_forwarders scopes.
• :has_role? that checks if a user is a particular type.
• :desk_worker?, :mail_forwarder that proxy to :has_role?.
• :has_roles? that checks if a user is of any of the types supplied.

And creates classes DeskWorker and MailForwarder that:

• Inherit from User.
• Have default scopes for :desk_workers and :mail_forwarders respectively.
• Create users with the right associated occupation.

To configure the other end of the association, add guise_for:

class Guise < ActiveRecord::Base
  guise_for :user
end

This method does the following:

• Sets up belongs_to association and accepts the standard options.
• Validates the column storing the name of the guise in the list supplied is unique to the resource it belongs to and is one of the provided names.

Customization

If the association doesn't fit what is assumed, you can pass in the options for has_many into has_guises. The same applies to guise_for with the addition that you can specify not to validate attributes

class Person < ActiveRecord::Base
  has_guises :Admin, :Engineer,
             :association => :positions,
             :attribute => :rank,
             :foreign_key => :employee_id,
             :class_name => :JobTitle
end

class JobTitle < ActiveRecord::Base
  guise_for :person,
            :foreign_key => :employee_id,
            :validate => false # skip setting up validations
end

The Future

• Provide generators for roles table
• Update has_guises method to setup has_many association
• Adding validations on guise_attribute column into association class