Machinist

Simple hierarchical state machines.

Install

With npm do:

npm install machinist

Examples

Turnstile

  var Machinist = require('machinist'),
      locked = Machinist(),
      unlocked = Machinist(),
      turnstile = Machinist(locked);

  turnstile.addTransition('insert coin', locked, unlocked);
  turnstile.addTransition('insert coin', unlocked, unlocked);
  turnstile.addTransition('push', unlocked, locked);
  turnstile.addTransition('push', locked, locked);

  console.log(turnstile.state); // locked
  turnstile.go('insert coin');
  console.log(turnstile.state); // unlocked
  turnstile.go('push');
  console.log(turnstile.state); // locked

Game State Manager

Machinist creates objects which are both machine and states. This allows you to create hierarchical state machines like this Game State Manager:

  var Machinist = require('machinist'),
      menu = Machinist(),
      play = Machinist(),
      pause = Machinist(),
      gameState = Machinist(menu);

  gameState.addTransition('play', menu, play);
  gameState.addTransition('menu', play, menu);

  play.addTransition('pause', null, pause);
  play.addTransition('play', pause, null);

  play.on('exit', function () {
    if (play.state === pause) {
      play.go('play');
    };
  });

  console.log(gameState.state); // menu
  console.log(play.state); // null
  gameState.go('play');
  console.log(gameState.state); // play
  console.log(play.state); // null
  play.go('pause');
  console.log(gameState.state); // play
  console.log(play.state); // pause
  play.go('menu');
  console.log(gameState.state); // menu
  console.log(play.state); // null

API

  var Machinist = require('machinist');

var machine = Machinist(initialState=null, cb=null)

Create a new Machinist object machine.

machine.state is set to initialState.

cb will be called before the intialState is transitioned to.

machine.state

Reference to the current state the machine is in.

machine.addTransition(name, from, to)

Creates a valid transition name that will switch from the state from to the state to.

Transitions must have a unique name and from parameters.

machine.go(name)

Executes the defined transition name. The transition must be added prior to being called.

machine.enter()

Signals the machine that it is being transitioned in to. You should not need to call this as it is taken care of internally when machine.go is called.

machine.exit()

Signals the machine that it is being transitioned away from. You should not need to call this as it is taken care of internally when machine.go is called.

machine.destroy()

Destroys the machine.

Events

state.on('enter', cb)

This event fires with cb(machine) when the machine is entered.

state.on('exit', cb)

This event fires with cb(machine) when the machine is exited.

machine.on('transition', cb)

This event fires with cb(transitionName, fromState, toState) when a transition is executed.

machine.on('transitionnotfound', cb)

This event fires with cb(transitionName) when a transition is called but a valid one does not exist for the machine go was called on.

machine.on('destroy', cb)

This event fires with cb(machine) when the machine is destroyed.

Users of a Machine should listen for the destroy event and clean up any references they hold so the Machine can be garbage collected.

Destroying a Machine will not destroy the machines it transitions between. To destroy them you should call their destroy method.

License

(The MIT License)

Copyright (c) 2014 RGBboy <[email protected]>

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.