Mouse Organ

Ladies and gentlemen, the Marvelous -- Mechanical -- Mouse Organ!

This is a very small mixin that turns a class into a basic state machine.

Installation

Just download lib/mouse_organ.rb into your code. Or you could just use it as a pattern of sorts, and roll your own in the same vein.

I mean, sure, you can also gem install mouse_organ. But honestly, it might be better to have the class where you can see it, for documentation purposes? Your call.

Example

class Foo
  include MouseOrgan

  def initialize
    machine_start(:one)
  end

  def state_one
    transition_to :two
    sleep 1
  end

  def state_two
    transition_to :three
    sleep 1
  end

  def state_three
    throw :machine_stop
  end

  def transition_to(state)
    puts state
    super
  end

end

What You Get

Each of your methods that start state_ define a state of the state machine. To start the machine, pass #machine_start the initial state name (e.g., :two for the state defined by #state_two).

Inside a state method, you can change to a new state using transition_to(:statename). You can stop the machine using throw :machine_stop, or you can override #machine_stop? to return true if the machine should stop.

Passing an invalid state to #machine_start or #transition_to raises ArgumentError.

The attribute @state holds the current state.

It might be useful to override #transition_to as I have above -- for example, in order to log every change of state.