"xxx_id may not be null" when saving many to many joined objects

Rails
#1

Hi,

I have two model classes; Tune and Title and they are joined in a many
to
many relationship through a Variation class. Here’s some stub code of
the
models:

class Tune < ActiveRecord::Base
has_many :variations, :dependent => :destroy
has_many :titles, :through => :variations
…
class Title < ActiveRecord::Base
has_many :variations, :dependent => :destroy
has_many :tunes, :through => :variations
…
class Variation < ActiveRecord::Base
belongs_to :tune
belongs_to :title
…

In my TunesController I create a new Tune, Variation and Title. I set
the
:tune and :title attributes in the Variation, and add the Variation to
the
tune and title’s :variations arrays.

The problem is that when I save the Tune, I get the following error:
SQLite3::SQLException: variations.title_id may not be NULL:
INSERT INTO “variations” (“updated_at”, “title_id”, “tune_id”,
“created_at”)
VALUES(‘2008-09-18 12:21:52’, NULL, NULL, ‘2008-09-18 12:21:52’)

I assumed that Rails would know that the Tune, Variation and Title are
all
new objects and perform the save of the Tune and Title, get their IDs to
store in the Variation and lastly save the Variation.

Any help or pointers for where to look are greatly appreciated.

Thanks,
Pat

View this message in context:
http://www.nabble.com/"xxx_id-may-not-be-null"-when-saving-many-to-many-joined-objects-tp19551721p19551721.html
Sent from the RubyOnRails Users mailing list archive at Nabble.com.

#2

Hi,

fixed the problem. I added the Variation to the ‘created’ Tune before
I had added the Title to the Variation. So the Variation obviously
didn’t have a Title object with which an id could be derived/created.

Cheers
Pat