In rails guides it's described like this: "Objects will be in addition destroyed if they’re associated with :dependent => :destroy, and deleted if they’re associated with :dependent => :delete_all."
Right, cool. But what's the difference between being destroyed and being deleted? I tried both and it seems to do the same thing.
The difference is with callback.
The :delete_all, made directly in your application the delete by SQL :
DELETE * FROM users where compagny_id = XXXX
With the :destroy, there are an instantiation of all of you children. So, if you can't destroy it or if each has their own :dependent, its can be called.
On a Rails' model association you can specify the :dependent option, which can take one of the following three forms:
:destroy/:destroy_all The associated objects are destroyed alongside this object by calling their destroy method:delete/:delete_all All associated objects are destroyed immediately without calling their :destroy method:nullify All associated objects' foreign keys are set to NULL without calling their save callbacks