Roles in Rails

gistfile1.rb

class User < ActiveRecord::Base

  ROLES = [:admin, :basic]

  scope :with_role, -> role { where("roles_mask & #{2**User::ROLES.index(role)} > 0") }  

  # Checks whether the roles passed in list are set for the instance.
  # @param [Array<Symbol>] roles The list of role symbols to check.
  def role?(*roles)
    self.roles.any? { |role| roles.include? role }
  end

  # Returns list of roles for the User.
  # @return [Array] The lost of role symbols currently set.
  def roles
    ROLES.reject do |r|
      ((roles_mask || 0) & 2**ROLES.index(r)).zero?
    end
  end

  # Converts roles to their equivalent roles mask and sets to the instance.
  # @note Watch out for splat implementations since the great splat disaster of 2011.
  # @param [Array<Symbol>] roles The list of role symbols to set.
  def roles=(roles)
    roles = roles.is_a?(Array) ? (roles.collect { |r| r.to_sym }) : [roles.to_sym]
    raise "You can't assign a role that doesn't exist" unless roles.all? {|role| ROLES.include? role}
    self.roles_mask = (roles & ROLES).map { |r| 2**ROLES.index(r) }.sum
  end
end