gistfile1.rb

    Shipment.class_eval do
      def editable_by?(user)
        %w(pending ready_to_ship unable_to_ship needs_fulfilment).include?(state) or user.has_role?(:admin)
      end
      
      Shipment.state_machines[:state] = StateMachine::Machine.new(Shipment, :initial => 'pending') do 
        event :ready do
          transition :from => 'pending', :to => 'ready_to_ship'
        end
        event :pend do
          transition :from => 'ready_to_ship', :to => 'pending'
        end
        event :ship do
          transition :from => ['needs_fulfilment', 'acknowledged'], :to => 'shipped'
        end
        event :transmit do 
          transition :from => 'ready_to_ship', :to => 'transmitted'
        end
        event :acknowledge do 
          transition :from => 'transmitted', :to => 'acknowledged'
        end
        event :flag do
          transition :from => 'ready_to_ship', :to => 'needs_fulfilment'
        end
        event :problem do
          transition :from => ['transmitted', 'acknowledged', 'needs_fulfilment'], :to => 'unable_to_ship'
        end
        after_transition :to => 'shipped', :do => :transition_order
      end       
    end