Rails - Jun 2006 - adding action after a belongs_to assignment

What is the best way to add action after a belongs_to assignment? (Just 
like ''after_add'' in has_many assignment).

I see that there is no callbacks for belongs_to.

I have tried overriding parent= :

alias :parent_before_mod= :parent
def parent=(the_parent)
  parent_before_mod = the_parent
  if save
    # my actions here
  end
end

but when I tried to assign parent, parent_id was not changed.

Can someone help?

class Company < ActiveRecord::Base
  has_many :children, :class_name => ''Company'',
:foreign_key =>
''parent_id'',
    :after_add => :after_add_child, :before_remove => 
:before_remove_child
  belongs_to :parent, :class_name => ''Company'',
:foreign_key =>
''parent_id''
  # something similar to :after_add above?
end

--
Endy

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