Setting association values via id or objects

Hi there,

I've got a question about best practice/preferred method of setting up
an association. I have a User model which has and belongs to many

From playing about with the console I know I can go..

interests = Interests.find([1,2,3,4])
user =>interests)
user =>[1,2,3,4,5])

and similarly on existing objects

user.interest_ids = [1,2,3,4]
or user.interests = [interest_obj_a, interest_obj_b, interest_obj_c)

My question is, is there a functional difference between the two, or
can one freely interchange between setting relations via id or via
literal objects?



There is no difference in the results, where there might be a difference
is in how many calls to the database each takes. Do which ever is more
straight forward to start, however. By the time it makes a performance
difference you may have ditched the HABTM relationship for something
saner anyway.