Rails - Feb 2006 - Rolled my own alternative to trigger function with OLD/NEW

Back with PostgreSQL, I just inspected OLD and NEW in trigger functions. 
I came up with this alternative in Rails:

class Item < ActiveRecord::Base

  def active=(value)
    self.set_old(''active'', self.active)

    write_attribute(:active, value)
  end

  def after_update
    if !get_old(''active'') and self.active
      Notifier::deliver_item_approved(self)
    end

    if get_old(''active'') != self.active
      Maintenance.delete_cache(''...'') # I wrote my own
alternative to
expire_fragment that actually works in models. Grumble...
    end
  end

  protected

  def get_old(value)
    @old[value] unless @old.nil?
  end

  def set_old(key, value)
    (@old ||= {})[key] = value
  end

end

Feel free to expound on it! I tested it out and didn''t get any nil 
errors (I''m still shaky with nils - I guess get_old defaults to false
if
@old[value] is nil?). I''m also clueless why making the get/set_old 
functions to private causes an error.

Joe

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