Question

I have a 3 column join table that is storing 3 ID’s for 3 different HABTM models.

Models

# ProductGrade.rb
has_and_belongs_to_many :vendors, :join_table => "item_codes_product_grades_vendors"
has_and_belongs_to_many :item_codes, :join_table => "item_codes_product_grades_vendors"

# Vendor.rb
has_and_belongs_to_many :prouduct_grades, :join_table => "item_codes_product_grades_vendors"
has_and_belongs_to_many :item_codes, :join_table => "item_codes_product_grades_vendors"

# ItemCode.rb
has_and_belongs_to_many :vendors, :join_table => "item_codes_product_grades_vendors"
has_and_belongs_to_many :product_grades, :join_table => "item_codes_product_grades_vendors"

I am simply wanting to record the 3-part association when a user updates on the Vendor model.

Vendors_Controller.rb

def update
  i = ItemCode.find(params[:vendor][:item_codes].to_i)
  i.vendors << Vendor.find(params[:id])
  i.product_grades << ProductGrade.find(params[:product_grade_id])

  redirect_to product_grade_vendor_path
end

This correctly saves the 3 columns of data in the join table, however it is creating two-different records, like this:

-- *product_grade_id* -- *vendor_id* -- *item_code_id* --
---------------------------------------------------------
--                12  --       NULL  --             4  --
--                12  --          6  --           NULL --

I realize this is probably a silly syntax issue, but I just want to know how to get the controller to save both of those values in 1 record.

Thanks for the help!

Answer 1

Consider using has_many :through => instead of HABTM. ActiveRecord can’t address join tables in HABTM but it can address join tables in has_many :through =>. With the later option, the join table will be represented as a model and you will be given tools how to manipulate it, change it, update it, etc.

I recommend using HABTM only when you are joining two models, but not three. Your update method will then be very much simplified.

def update
  Association.create!(:product_grade_id => "...", :vendor_id => "...", :item_code_id => "..."

  redirect_to wherever_path
end