state_machine

StateMachine::Integrations::DataMapper::Observer#after_transition_failure

Creates a callback that will be invoked *after* a transition failures to
be performed so long as the given requirements match the transition.

== Example

  class Vehicle
    include DataMapper::Resource
    
    property :id, Serial
    property :state, :String
    
    state_machine :initial => :parked do
      event :ignite do
        transition :parked => :idling
      end
    end
  end
  
  class VehicleObserver
    after_transition_failure do |transition|
      # log failure
    end
    
    after_transition_failure :on => :ignite do
      # log failure
    end
  end

See +before_transition+ for a description of the possible configurations
for defining callbacks.  *Note* however that you cannot define the state
requirements in these callbacks.  You may only define event requirements.

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