Handling database table dependencies

Hey,

thanks for reading this post. How do you handle dependencies? A really
simple example: I’ve got a table called “entity” and another table,
let’s say, “entity_type”. The entity types can be changed, of course,
they also should be deletable, but only, if they are not used by some
entities! How can I ensure this in Rails or directly in the DBMS
(postgres)? Do I have to check it manually within a validate-method in
the model?

Thanks for any suggestions!

Cheers, ms

Are you talking about a polymorphic association??

You can set that up simply enough in the models after doing a wee
search on them,

http://envycasts.com/products/advanced-activerecord

May have some interesting insight into them, it would then be easy
enough to create a method from a before_destroy callback to check if
it is being used or not…

Cheers

Richard

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