foreign key constraints vs. association_dependencies

[benhutton]

We're a little late to the game adding foreign key constraints. Our app is built with heavy use of the association_dependencies plugin. Is a foreign key constraint with a properly configured on_delete better than using the association_dependencies plugin? Is there any reason you'd still use association_dependencies even with the foreign key constraint on_delete?

[jeremyevans]

Assuming that the foreign key ON DELETE behavior is what you want, it's probably better than using association_dependencies. For one, foreign key ON DELETE will handle all database changes, not just those that occur via the model layer. association_dependencies can do this that foreign_key ON DELETE cannot handle, such as using the :destroy option to call the model level destroy (which can call before/after destroy hooks), so if you need that, that's a possible reason to continue using associaiton_dependencies.