cheat sheets.

== Example

class Order < ActiveRecord::Base
  acts_as_state_machine :initial => :opened

  state :opened
  state :closed, :enter => Proc.new {|o| Mailer.send_notice(o)}
  state :returned

  event :close do
    transitions :to => :closed, :from => :opened
  end

  event :return do
    transitions :to => :returned, :from => :closed
  end
end

o = Order.create
o.close! # notice is sent by mailer
o.return!