# Noob stuck - complex model relationships and one of two foreign keys not getting saved or updated **URL:** \ **Category:** Rails\ **Created:** [March 16, 2010, 11:23pm UTC](https://www.ruby-forum.com/t/noob-stuck-complex-model-relationships-and-one-of-two-foreign-keys-not-getting-saved-or-updated/185257 "2010-03-16T23:23:07Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![ander31415](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ed655f/32.png) [@ander31415](https://www.ruby-forum.com/u/ander31415)\ **Post date:** [March 16, 2010, 11:23pm UTC](https://www.ruby-forum.com/t/noob-stuck-complex-model-relationships-and-one-of-two-foreign-keys-not-getting-saved-or-updated/185257/1 "2010-03-16T23:23:07Z")
Rather than posting my code and asking “what’s wrong”, here’s a simpler version: The problem is my C’s are not saving or updating the foreign key for B when I create or update a C. The foreign key value remains nil. A has many Bs A has many Cs B has many Cs B belongs to A The B model contains an A\_id foreign key field C belongs to A C belongs to B The C model contains both A\_id and B\_id foreign key fields So a C can either belong directly to A (with B being null) or it can belong to both an A and B. This is not a C belongs to A through B relationship - Cs can belong directly to an A. Cs are created using current\_A.Bs.new, so they are already automatically scoped to the correct A. When creating or editing a C, a table of possible Bs is created and displays correctly and I am able to select one of the possible choices or leave it set to the default (‘none selected’ / nil value) choice. This all worked fine before I layered on the A model. I was able to create Cs that were either free standing or belonged to a B. Now, the terminal console shows the URL string contains: “B\_id”=\>“15”, so it appears that the select function is grabbing the correct id from the table for the B choice that was selected. However, when I then debug the updated C record, the B\_id value is always nil. So, why isn’t the B\_id field getting updated in this situation? Thanks in advance. ---
**Author:** ![ander31415](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ed655f/32.png) [@ander31415](https://www.ruby-forum.com/u/ander31415)\ **Post date:** [March 16, 2010, 11:23pm UTC](https://www.ruby-forum.com/t/noob-stuck-complex-model-relationships-and-one-of-two-foreign-keys-not-getting-saved-or-updated/185257/2 "2010-03-16T23:23:42Z")
On Mar 16, 5:47 pm, ander31415 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Now, the terminal console shows the URL string contains: “B\_id”=\>“15”, > so it appears that the select function is grabbing the correct id from > the table for the B choice that was selected. However, when I then > debug the updated C record, the B\_id value is always nil. > > So, why isn’t the B\_id field getting updated in this situation? Hard to say without seeing what you’re actually doing. I know you’ve deliberately not posted code, but without code, unless your basic premise is fundamentally flawed it’s just guesswork. Fred ---
**Author:** ![ander31415](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/ed655f/32.png) [@ander31415](https://www.ruby-forum.com/u/ander31415)\ **Post date:** [March 17, 2010, 12:46am UTC](https://www.ruby-forum.com/t/noob-stuck-complex-model-relationships-and-one-of-two-foreign-keys-not-getting-saved-or-updated/185257/3 "2010-03-17T00:46:12Z")
My error (Noob!) - the model for C had set attr\_protected for the B\_id field. So Rails was doing exactly as I instructed it. I found this by reviewing the development log, which included a warning that B\_id was protected against mass updates. Thanks all. On Mar 16, 3:13 pm, Frederick C. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On Mar 16, 5:47 pm, ander31415 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > \*\*\* CUT \*\*\*