问将代码注入ruby状态机？

EN

class Artifact < ActiveRecord::Base
  include Provisionable # << This module makes the magic method 'provision',
                        # << below, available

  state_machine :machine_state, :initial => :s_initial do
    # ...
    provision(:param1, :param2, :param3) # << The Question: how to define
                                         # << this in the Provisionable mixin
                                         # << module, below
    ...
  end
...
end

module Provisionable
  #
  # << provision() is supposed to inject the desired code into the state machine:
  #
  def provision

    # << Code sample to be injected begins here:
    event :parameterize do
      transition :s_unprovisioned => :s_initial
    end
    before_transition :s_unprovisioned => :s_initial do |artifact, transition|
      transition.args.each_pair do |param, value|
        # etc...
      end
    end
    # >> Code to be injected ends here.

  end
end

StateMachine::Machine.class_eval do
    def inject_provisioning()

        event :start do
            transition :s_initial => :s_provisioning
        end
        after_transition :s_initial => :s_provisioning do |goal, transition|
            # Do useful stuff here
            true
        end

        event :provision do
            transition :s_provisioning => :s_completed
        end

        before_transition :s_provisioning => :s_completed do |goal, transition|
            artifact_type = transition.args[0]
            params = transition.args[1]
            # Useful stuff here
            true
        end

        after_transition :s_provisioning => :s_completed do |goal, transition|
            artifact_type = transition.args[0]
            params = transition.args[1]
            # Useful stuff here
        end
    end

    def inject_expiration()
        event :chron do
            expired_callback = lambda \
                do |goal|
                    return false if goal.expires_at == :never
                    goal.expires_at.to_i < DateTime.now.to_i
                end
            active_callback = lambda \
                do |goal|
                    return true if goal.expires_at == :never
                    goal.expires_at.to_i >= DateTime.now.to_i
                end
            transition all - :s_expired => :s_expired, :if => expired_callback
        end

        before_transition all - :s_expired => :s_expired do |goal, transition|
            goal.undo
        end
    end

state_machine :machine_state, :initial => :s_initial do
    inject_provisioning
    inject_expiration
end