# Why no :dependent =\> :destroy on belongs\_to?

**URL:** <https://www.ruby-forum.com/t/why-no-dependent-destroy-on-belongs-to/109383>\
**Category:** Rails\
**Created:** [July 13, 2007, 10:31pm UTC](https://www.ruby-forum.com/t/why-no-dependent-destroy-on-belongs-to/109383 "2007-07-13T22:31:08Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![chase](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/76d3ee/32.png) [@chase](https://www.ruby-forum.com/u/chase)\
**Post date:** [July 13, 2007, 10:31pm UTC](https://www.ruby-forum.com/t/why-no-dependent-destroy-on-belongs-to/109383/1 "2007-07-13T22:31:08Z")

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class Animal \< ActiveRecord::Base  
belongs\_to :species, :polymorphic =\> true  
end

class Goat \< ActiveRecord::Base  
has\_one :animal, :as =\> :species  
end

class Capybara \< ActiveRecord::Base  
has\_one :animal, :as =\> :species  
end

Polymorphic associations here, with goats and capybaras as types of  
animals. As usual, there is exactly one Animal record for every Goat or  
Capybara record. There should never be an Animal record without a  
species-specific counterpart, and vice-versa.

Just as the records are created in pairs, I want them to be deleted in  
pairs. If I was always acting on the species, this would be easy. Just  
change my models to:

class Goat \< ActiveRecord::Base  
has\_one :animal, :as =\> :species, :dependent =\> :destroy  
end

class Capybara \< ActiveRecord::Base  
has\_one :animal, :as =\> :species, :dependent =\> :destroy  
end

and henceforth, myGoat.destroy also accomplishes myGoat.animal.destroy.  
But what about the other side of the association? myAnimal.destroy  
should accomplish myAnimal.species.destroy. I try:

class Animal \< ActiveRecord::Base  
belongs\_to :species, :polymorphic =\> true, :dependent =\> :destroy  
end

but the dependent option is ignored. Is there any motivated reason why  
belongs\_to lacks the :dependent option? Admittedly, the workaround is  
really simple:

class Animal \< ActiveRecord::Base  
belongs\_to :species, :polymorphic =\> true  
before\_destroy {|animal| animal.species.destroy }  
end

but the consistency of the :dependent syntax would be nice.

Also: is there any way to ensure that destroying _either_ half of the  
association destroys the whole association? I can only seem to plug the  
problem from one side at a time (sending both side’s destroy methods to  
each other creates an infinite loop).

A similar previous discussion: [Polymorphic destroy of resource - Rails - Ruby-Forum](http://www.ruby-forum.com/topic/105893)