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

The only changes I’ve made are creating more callbacks with slightly more obvious semantics ;).

The callback chain & order on a successful event looks like:

oldstate:exit*
event:before
__find transition, if possible__
transition:on_transition*
newstate:enter*
oldstate:before_exit
newstate:before_enter
__update state__
oldstate:after_exit
oldstate:after_enter
event:after
event:success*
obj:aasm_event_fired*

(*) marks old callbacks

Note that the old callbacks haven’t been removed and still have their same semantics. All of this behavior was added without removing any old behavior.

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

• github.com/dunedain289/aasm/tree/master

% sudo gem sources -a http://gems.github.com # (you only need to do this once)
% sudo gem install dunedain289-aasm

% rake gem
% sudo gem install pkg/aasm-2.1.gem

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

class Conversation
  include AASM

  aasm_initial_state :unread

  aasm_state :unread
  aasm_state :read
  aasm_state :closed

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

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

Author

Scott Barron <scott at elitists dot net>

License

Original code Copyright 2006, 2007, 2008 by Scott Barron. New changes Copyright 2009 by Scott Petersen. Released under an MIT-style license. See the LICENSE file included in the distribution.

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.