You can get a full list of the ActiveRecord callbacks here.

Callbacks are a handy way of insuring specific behaviors on your models as well as managing the events that follow the callbacks.

For example, a before_destroy callback can be called to destroy associated objects. (This is best done on the association with :dependent => :destroy, but it makes sense here too.)

You can also stop the destroy process if you have dependent objects you can’t destroy by returning false.

I’ve used ActiveRecord Callbacks to:

Set default values

Format specific fields (like phone numbers)

Send emails when an object is updated or deleted

Create child objects from comma delimited lists in a string

Change an object’s state