Question

I have 2 tables, products and codes. Products has a code_str column. I can find a Code from a product by using the first 2 characters of the products.code_str column. I’ve tried doing something like this:

class Product < ActiveRecord::Base
  belongs_to :code, foreign_key: "substring(products.code_str from 1 for 2)", primary_key: :number
end

But it doesn’t work. I’d like to use some eager loading in the future, so I thought on making a belongs_to association work instead of anything else.

Any ideas?

Answer 1

Had the same problem.

At the end added:

belongs_to :code, foreign_key: :code_str_id, primary_key: :number

def code_str_id
  code_str[0..1]
end

Pros: finds each and works with include

Cons: Queries are slow when using include