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Edge State Machine is a complete state machine solution. It offers support for ActiveRecord, Mongoid and MongoMapper for persistence.
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Edge State Machine¶ ↑

Edge State Machine is a complete state machine solution. It offers support for ActiveRecord, Mongoid and MongoMapper for persistence.

<img src=“https://secure.travis-ci.org/danpersa/edge-state-machine.png”/>

Supported Features¶ ↑

  • Multiple state machines per class each of them acting independently

  • Find errors in state machine definitions as early as possible

  • Transition guards

  • Multiple actions executed on transitions

  • Multiple actions executed on entering and exiting a state

  • No other dependencies for non-persistent state machines

  • Minimal dependencies for persistent ones

Installation¶ ↑

If you’re using Rails + ActiveRecord + Bundler

# in your Gemfile
gem "edge-state-machine", :require => ["edge-state-machine", "active_record/edge-state-machine"]

# in your AR models that will use the state machine
include ::EdgeStateMachine
include ActiveRecord::EdgeStateMachine

state_machine do
  state :available # first one is initial state
  state :out_of_stock
  state :discontinue

  event :discontinue do
    transitions :to => :discontinue, :from => [:available, :out_of_stock], :on_transition => :do_discontinue
  end
  event :out_of_stock do
    transitions :to => :out_of_stock, :from => [:available, :discontinue]
  end
  event :available do
    transitions :to => :available, :from => [:out_of_stock], :on_transition => :send_alerts
  end
end

If you’re using Rails + Mongoid + Bundler

# in your Gemfile
gem "edge-state-machine", :require => ["edge-state-machine", "mongoid/edge-state-machine"]

# in your AR models that will use the state machine
include ::EdgeStateMachine
include Mongoid::EdgeStateMachine

state_machine do
  state :available # first one is initial state
  state :out_of_stock
  state :discontinue

  event :discontinue do
    transitions :to => :discontinue, :from => [:available, :out_of_stock], :on_transition => :do_discontinue
  end
  event :out_of_stock do
    transitions :to => :out_of_stock, :from => [:available, :discontinue]
  end
  event :available do
    transitions :to => :available, :from => [:out_of_stock], :on_transition => :send_alerts
  end
end

If you’re using Rails + MongoMapper + Bundler

# in your Gemfile
gem "edge-state-machine", :require => ["edge-state-machine", "mongo_mapper/edge-state-machine"]

# in your models that will use the state machine
include ::EdgeStateMachine
include MongoMapper::EdgeStateMachine

state_machine do
  state :available # first one is initial state
  state :out_of_stock
  state :discontinue

  event :discontinue do
    transitions :to => :discontinue, :from => [:available, :out_of_stock], :on_transition => :do_discontinue
  end
  event :out_of_stock do
    transitions :to => :out_of_stock, :from => [:available, :discontinue]
  end
  event :available do
    transitions :to => :available, :from => [:out_of_stock], :on_transition => :send_alerts
  end
end

State Machine Examples¶ ↑

Microwave State Machine¶ ↑

class Microwave
  state_machine :microwave do  # name should be optional, if the name is not present, it should have a default name
                               # we give state machines names, so we can pun many machines inside a class
    initial_state :unplugged # initial state should be optional, if the initial state is not present, the initial state will be the first defined state

    state :unplugged

    state :plugged

    state :door_opened do
      enter :light_on            # enter should be executed on entering the state
      exit  :light_off           # exit method should be executed on exiting the state
    end

    state :door_closed

    state :started_in_grill_mode do
      enter lambda { |t| p "Entering hate" }   # should have support for Procs
      exit  :grill_off
    end

    state :started do
      enter :microwaves_on
      exit  :microwaves_off
    end

    event :plug_in do
      transition :from => :unplugged, :to => :plugged
    end

    event :open_door do
      transition :from => :plugged, :to => :door_opened
    end

    event :close_door do
      transition :from => :door_opened, :to => :door_closed,
                 :on_transition => :put_food_in_the_microwave # we can put many actions in an Array for the on_transition parameter
    end

    event :start do
      transition :from => :door_closed, :to => [:started, :started_in_grill_mode],
                 :on_transition => :start_spinning_the_food,
                 :guard => :grill_button_pressed?    # the method grill_button_pressed? should choose the next state
    end

    event :stop do
        transition :from => [:started, :started_in_grill_mode], :to => :door_closed
    end
  end  
end

Dice State Machine¶ ↑

class Dice

  state_machine do
    state :one
    state :two
    state :three
    state :four
    state :five
    state :six

    event :roll do
      transition :from => [:one, :two, :three, :four, :five, :six],
                 :to => [:one, :two, :three, :four, :five, :six],
                 :guard => :roll_result,
                 :on_transition => :display_dice_rolling_animation
    end
  end

  def roll_result
    # return one of the states
  end

  def display_dice_rolling_animation
    # draw the new position of the dice
  end
end

class User
  state_machine do
    state :pending # first one is initial state
    state :active
    state :blocked # the user in this state can't sign in

    event :activate do
      transition :from => [:pending], :to => :active, :on_transition => :do_activate
    end

    event :block do
      transition :from => [:pending, :active], :to => :blocked
    end
  end    
end

Other Examples¶ ↑

For other (more complex) examples, please check the following links:

Notes¶ ↑

For classes with multiple state machines, the state names, machine names must be unique per class.

The same thing with the event names.

Credits¶ ↑

The gem is based on Rick Olson’s code of ActiveModel::StateMachine, axed from ActiveModel in this commit.

And on Krzysiek Heród’s gem, Transitions, which added Mongoid support.