Registrable

require 'registrable'

module Plugin

  extend Registrable

  class Base
    def self.inherited(subclass)
      identifier = subclass.to_s
        .split('::').last
        .gsub(/([a-z0-9])([A-Z])/, '\1_\2')
        .downcase.to_sym

      Plugin.register(identifier, subclass)
    end
  end

end

class MyPlugin < Plugin::Base; end
class AnotherPlugin < Plugin::Base; end

p Plugin.registry.keys                              # => [:my_plugin, :another_plugin]
p Plugin.registry[:my_plugin] == MyPlugin           # => true
p Plugin.registry[:another_plugin] == AnotherPlugin # => true

require 'registrable'

class Role

  extend Registrable

  def initialize(readable, modify)
    @readable, @modifiable = readable, modifiable
  end

  def readable?
    @readable
  end

  def modifiable?
    @modifiable
  end

end

class User

  def initialize(role)
    self.role = role
  end

  attr_reader :role

  def role=(role)
    role = Role.registry[role] || Role.registry[:other] unless role.is_a?(Role)

    @role = role
  end

end

Role.register(:other, Role.new(false, false))
Role.register(:user,  Role.new(true,  false))
Role.register(:admin, Role.new(true,  true))

other = User.new(:other)

p other.role.readable?   # => true
p other.role.modifiable? # => true

user = User.new(:user)

p admin.role.readable?   # => true
p admin.role.modifiable? # => false

admin = User.new(:admin)

p admin.role.readable?   # => true
p admin.role.modifiable? # => true