Rails - Dec 2008 - Callback when objects connect as a habtm relationship

If Product and Category models are in a habtm relationship, i.e.

class Product < ActiveRecord::Base
  has_and_belongs_to_many :categories
end

class Category < ActiveRecord::Base
  has_and_belongs_to_many :products
end

I want a piece of code to be executed every time a product is connected to a
category.
Where do I put this code? Which callback (and on which model) will be
triggered?

Any hints appreciated. Thanks for help.

-- 
- Kazim Zaidi
Blog: http://tuxplayground.blogspot.com

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Kazim Zaidi wrote:
> If Product and Category models are in a habtm relationship, i.e.
> 
> class Product < ActiveRecord::Base
>   has_and_belongs_to_many :categories
> end
> 
> class Category < ActiveRecord::Base
>   has_and_belongs_to_many :products
> end
> 
> I want a piece of code to be executed every time a product is connected 
> to a category.
> Where do I put this code? Which callback (and on which model) will be 
> triggered?
Look into adding :after_add callbacks to the associations:

http://api.rubyonrails.com/classes/ActiveRecord/Associations/ClassMethods.html#M001602


-- 
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