Moody: An implementation of the State Pattern in ruby

This is an object-oriented way to represent Finite State Machines, where an object can change its behavior at runtime, depending on its internal state.

If you want more information about this pattern, read the explanation by SourceMaking.

For a stupid example of how you would use this, here is a traffic light:

class Stop < Moody::State
  def color
    "red"
  end

  def next
    sleep 3
    switch_to Go
  end

  def enter
    # turn on camera tu see who crosses on a red light
  end

  def leave
    # turn off camera
  end
end

class Go < Moody::State
  def color
    "green"
  end

  def next
    sleep 2
    switch_to Caution
  end
end

class Caution < Moody::State
  def color
    "yellow"
  end

  def next
    sleep 1
    switch_to Stop
  end
end

class TrafficLight
  extend  Moody::Context

  initial_state Stop
  delegate_to_state :color, :next
end

traffic_light - TrafficLight.new

loop do
  puts traffic_light.color
  traffic_light.next
end

Callbacks

As you can see from the example above, Moody also provides callbacks when entering and leaving a state. If your state classes define instance methods enter and leave, then they will be called at the appropriate times.

Inspiration

This is a reimplementation of the State Pattern gem by Daniel Cadenas. Check out his implementation at his repository.

Installing

gem install moody

Contributing

• Send a pull request.
• Small, atomic commits, please.
• Make sure to add tests.
• Bonus points if you add features on topic branches.

License

Copyright Nicolás Sanguinetti hi@nicolassanguinetti.info

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.