Just some playing around with a state machine representing a door that can lock, with "locked" being a separate state from "closed"

door-irb-output.log

sub@asdf:~/projects/fsm$ irb -I
irb(main):001:0> require './door.rb'
=> true
irb(main):002:0> front_door = Door.new
=> #<Door:0x00000001913ab0 @state="closed">
irb(main):003:0> front_door.open_
Transition: closed => open
=> true
irb(main):004:0> front_door.close
Transition: open => closed
=> true
irb(main):005:0> front_door.lock
Transition: closed => locked
=> true
irb(main):006:0> front_door.open_
=> false
irb(main):007:0> front_door.close
=> false
irb(main):008:0> front_door.unlock
Transition: locked => closed
=> true
irb(main):009:0> front_door.close
=> false
irb(main):010:0> front_door.open_
Transition: closed => open
=> true
irb(main):011:0>

door.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'bundler/setup'

require 'state_machine'

class Door
  state_machine :state, :initial => :closed do
    after_transition any => any do |door, transition|
      puts "Transition: #{transition.from} => #{transition.to}"
    end

    event :open_ do
      transition :closed => :open
    end

    event :close do
      transition :open => :closed
    end

    event :lock do
      transition :closed => :locked
    end

    event :unlock do
      transition :locked => :closed
    end
  end
end