A precursor of http://github.com/henrik/autho.

user_session.rb

# https://github.com/barsoom/attr_extras
require "attr_extras"

class UserSession
  pattr_initialize :controller, :session_key, :finder

  # NOTE: Not memoized yet.
  def user
    if id
      finder.find(id)
    else
      nil
    end
  end

  def user=(user)
    controller.session[session_key] = user.id
  end

  def clear
    controller.session[session_key] = nil
  end

  private

  def id
    controller.session[session_key]
  end
end