Rails/ActiveRecord: save changes to a model's associated collections

Question

Do I have to save modifications to individual items in a collection for a model, or is there a method I can call to save them when I save the model.

#save

Answer 1

just do a rental.dvd.save after you increment the value or in the above case you could use

rental.dvd.increment!(:copies)

which will also automatically save, note the '!' on increment!