state_machine

https://github.com/pluginaweek/state_machine

Ruby

Adds support for creating state machines for attributes on any Ruby class

StateMachine::EventCollection#valid_for

Gets the list of events that can be fired on the given object.

Valid requirement options:
* <tt>:from</tt> - One or more states being transitioned from.  If none
  are specified, then this will be the object's current state.
* <tt>:to</tt> - One or more states being transitioned to.  If none are
  specified, then this will match any to state.
* <tt>:on</tt> - One or more events that fire the transition.  If none
  are specified, then this will match any event.
* <tt>:guard</tt> - Whether to guard transitions with the if/unless
  conditionals defined for each one.  Default is true.

== Examples

  class Vehicle
    state_machine :initial => :parked do
      event :park do
        transition :idling => :parked
      end
      
      event :ignite do
        transition :parked => :idling
      end
    end
  end
  
  events = Vehicle.state_machine(:state).events
  
  vehicle = Vehicle.new               # => #<Vehicle:0xb7c464b0 @state="parked">
  events.valid_for(vehicle)           # => [#<StateMachine::Event name=:ignite transitions=[:parked => :idling]>]
  
  vehicle.state = 'idling'
  events.valid_for(vehicle)           # => [#<StateMachine::Event name=:park transitions=[:idling => :parked]>]

Source | Google | Stack overflow

Edit

git clone [email protected]:pluginaweek/state_machine.git
cd state_machine
open lib/state_machine/event_collection.rb

Contribute

# Make a new branch
git checkout -b -your-name--update-docs-StateMachine--EventCollection-valid_for-for-pr

# Commit to git
git add lib/state_machine/event_collection.rbgit commit -m "better docs for StateMachine::EventCollection#valid_for"

# Open pull request
gem install hub # on a mac you can `brew install hub`
hub fork
git push <your name> -your-name--update-docs-StateMachine--EventCollection-valid_for-for-pr
hub pull-request

# Celebrate!