.build method not creating association in the join table

Question

I have three Models setup with the following associations

class User < ActiveRecord::Base has_many :faculties has_many :schools, :through => :faculties end class School < ActiveRecord::Base has_many :faculties has_many :users, :through => :faculties end class Faculty < ActiveRecord::Base belongs_to :user belongs_to :school end

and in my controller i go to create a school and assign the user

class SchoolsController < ApplicationController def create @school = current_user.schools.build(params[:school]) ... end end

When I login and submit the form the flash displays success, but the association doesn't build on the join table.

I tried it inside the apps console and it builds the association just fine.

I've been stuck on this for a couple days now and I just cannot figure out what I am missing. Thank in advance for any and all advice

can you show the log of what happens when the create action happens? — Msencenb
– Msencenb, Commented Jan 14, 2012 at 8:45

Wahaj Ali · Accepted Answer · 2012-01-14 08:11:58Z

1

The build method does not save the object. You need to explicitly call @school.save.

answered Jan 14, 2012 at 8:11

Wahaj Ali

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Comments

Jason Lewis · Accepted Answer · 2012-01-14 08:16:15Z

Two things: If the schools association is :through a has_many association, you will have to select which parent the School exists through.

So, for instance, if you were to nest School resources under users as in /users/:id/faculties/:id you could create a school via current_user.faculties.find(params[:faculty_id]).schools.build(params[:school]).save

Based on the example code, it looks like the fundamental problem is that the has_many xxx, :through syntax is being used without specifying the id of the faculties record. Remember two things: 1) ActiveRecord doesn't natively support composite primary keys, and 2) you must call #save on associated records created using #build. If you remember these, you should be fine.

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