Question

Assuming User has_one :subscription, Subscription belongs_to :user, and I am using accepts_nested_attributes_for to nest subscription attributes into the user creation form, what is the best way to locate and update and existing subscription (if it exists) based on User.email == Subscription.email?

Note that existing subscriptions could have user_id = nil

Answer 1

Probably what you want to do is use the email as the foreign key:

class User < ActiveRecord::Base
  has_one :subscription, :foreign_key => "email", :primary_key => "email"
end