Example of State pattern

state_pattern.rb

# gem install state_pattern
require 'state_pattern'

class Stop < StatePattern::State
  def next
    sleep 4
    transition_to(Go)
  end

  def color
    "Red (four sec...)"
  end
end

class Go < StatePattern::State
  def next
    sleep 2
    transition_to(Caution)
  end

  def color
    "Green (two sec...)"
  end
end

class Caution < StatePattern::State
  def next
    sleep 1
    transition_to(Stop)
  end

  def color
    "Yellow (one sec...)"
  end
end

class TrafficLight
  include StatePattern
  set_initial_state Stop
end

traffic_light = TrafficLight.new

loop do
  puts traffic_light.color
  traffic_light.next
end