Error: Unknown attribute in ActiveRecord(ruby). How to fix?

Question

Ruby on Rails

Hello.
There are the following models:

class Contractor < User<br>
  has_many :contractorEs<br>
  has_many :customers<br>
end<br><br>
class Customer < User<br>
  belongs_to :contractor<br>
  has_many :customerEs<br>
end<br>

There is a migration:

class AddContractorIdToCustomers < ActiveRecord::Migration<br>
  def change<br>
    add_column :customers, :contractor_id, :integer<br>
  end<br>
end<br>

I'm trying to create a customer (Customer), for this I go to the console and do the following:

c = Contractor.first<br>
c.customers.build<br>

Instead of the created customer, I get the following error message:

ActiveRecord::UnknownAttributeError: unknown attribute: contractor_id<br>

Migration started, the server restarted. The problem, unfortunately, remains.
Please tell me what could be causing this and how to fix it.
Rays of good to you :)
UPD: Ruby 2/Rails 4
UPD 2: I use STI, everything is inherited from User-a. Maybe the problem is related to this?
UPD 3: I continue to investigate the problem. It turned out that when creating a model through Customer.new, there is no contractor_id in the fields:

<Customer id: nil, first_name: nil, last_name: nil, address: nil, country: nil, zip: nil, city: nil, phone: nil, company_name: nil, signature: nil, type: "Customer", created_at: nil, updated_at: nil, v_token: nil, password_digest: nil, u_token: nil, email: nil, state: "new"><br>

If I inherit Customer from ActiveRecord::Base, then everything works fine. But I need to inherit from User.

Answer 1

strong_params?

 def contractor_params
    params.require(:contractor).permit(:contractior_id)
 end

Answer 2

what version of rails? if 3, then perhaps you need to add it to Customer

attr_accessible :contractor_id

Answer 3

replace

has_many :contractorEs

on the

has_many :contractors

and you will be happy

Answer 4

try making a has_many :through association, http://www.rusrails.ru/active-record-associations, and when migrating it's better to use contactor:references:index