gistfile1.rb

class Post < ActiveRecord::Base
  cattr_accessor :state_from, :state_to

  include ActiveSupport::Callbacks
  define_callbacks :after_transition

  #kod ....
  #(...)
    aasm_event :view, :enter => :enter, :exit => :exit, :success => :success do
      transitions :to => :read, :from => [:unread]
    end
  #(...)
  def success
    callback :after_transition
  end
  def exit
    self.state=self.aasm_state
  end
end

gistfile2.rb

class PostObserver < ActiveRecord::Observer
        def after_transition(article)
            p 'lol'
            LOG.warn("after_save #{article.to_yaml}")
        end
end