observer.rb

def notify_of_deal_state_change
    return unless state_changed?

    Deal.changed

    case state
    when 'closed'
      Deal.notify_observers 'deal_closed', self
    when 'rejected'
      Deal.notify_observers 'deal_rejected', self
    when 'pending'
      Deal.notify_observers 'deal_reopened', self
    end
  end