gistfile1.rb

class Ability
  include CanCan::Ability

  def initialize(user)
    return if user.nil?
    
    # Collect rights from roles
    authorizations = HashWithIndifferentAccess.new []
    user.roles.each do |role|
      role.resource_rights.each { |resource,actions| authorizations[resource] |= actions }
    end
    
    # Grant rights
    authorizations.each { |resource,actions| can actions, resource.to_s.classify.constantize }
  end

end