AASM - Ruby state machines

This package contains AASM, a library for adding finite state machines to Ruby classes.

AASM started as the acts_as_state_machine plugin but has evolved into a more generic library that no longer targets only ActiveRecord models.

AASM has the following features:

• States

• Machines

• Events

• Transitions

Download

The latest AASM can currently be pulled from the git repository on github.

• github.com/rubyist/aasm/tree/master

A release and a gem are forthcoming.

Installation

From GitHub hosted gems

% sudo gem sources -a http://gems.github.com # (you only need to do this once)
% sudo gem install rubyist-aasm

Building your own gems

% rake gem
% sudo gem install pkg/aasm-2.0.1.gem

Simple Example

Here’s a quick example highlighting some of the features.

class Conversation
  include AASM

  aasm_initial_state :initial

  aasm_state :initial
  aasm_state :read
  aasm_state :closed

  aasm_event :view do
    transitions :to => :read, :from => [:initial]
  end

  aasm_event :close do
    transitions :to => :closed, :from => [:read, :initial]
  end
end

Multiple transitions for an event are supported, in which case you want to specify a :guard option which is a symbol to a method or a proc that returns a boolean to decide whether that transition is allowed. aasm will process transitions in order and the first passing guard clause is the one in effect.

States also support :enter and :exit options allowing you further hooks into the lifecycle.

Advanced Features

Arguments to an event call will be passed to on_transition method.

aasm_event :view do transitions :to => :read, :from => [:initial], :on_transition => :view_happening end

def view_happening(a=nil, b=nil) end

Calling conversation.view(1, 2) will result in view_happening receiving a=1, b=2

UNLESS… You are using the advanced feature of multiple :to states in which case you can pass the state name symbol as the first argument to the event call to control your destination state.

aasm_event :view do transitions :to => [:read, :closed], :from => [:initial], :on_transition => :view_happening end

Now, you can call: conversation.view -> to transition to the first :to state (:read) or conversation.view :closed -> to force a transition to the :closed state or conversation.view(1, 2) -> to transition to :read and receive a=1, b=2 in view_happening or conversation.view(:closed, 1, 2) -> to transition to :closed and receive a=1, b=2 in view_happening

Other Stuff

Author

Scott Barron <scott at elitists dot net>

License

Copyright 2006, 2007, 2008 by Scott Barron. Released under an MIT-style license. See the LICENSE file included in the distribution.

Bugs

rubyist.lighthouseapp.com/projects/13207-aasm/

GitHub

github.com/rubyist/aasm/tree/master

Warranty

This software is provided “as is” and without any express or implied warranties, including, without limitation, the implied warranties of merchantibility and fitness for a particular purpose.