Demonstrates a possible technique for running events / defining callbacks

vehicle.rb

class Vehicle
  attr_accessor :running
  
  state_machine :initial => :parked do
    after_transition {|object, transition| object.send(transition.event)}
    
    event :ignite do
      transition :parked => :idling
    end
  end
  
  def ignite
    self.running = true
  end
end

v = Vehicle.new         # => #<Vehicle:0xb722506c @state="parked">
v.state                 # => "parked"
v.running               # => nil
v.fire_events(:ignite)  # => true
v.state                 # => "idling"
v.running               # => true