Rails sequence column on Model - ruby-on-rails

Question

I followed this mini-tutorial successfully to have a column (car_code) in my table (cars) to work like a sequence (using postgreSQL database).
As Result I have this table:
CREATE TABLE Cars
(
id serial NOT NULL,
created_at timestamp without time zone NOT NULL,
updated_at timestamp without time zone NOT NULL,
car_date timestamp without time zone,
car_code integer DEFAULT nextval('car_code_sequence'::regclass),
CONSTRAINT cars_pkey PRIMARY KEY (id )
)
My insert statement works fine:
INSERT INTO cars(created_at, updated_at, car_date) VALUES (now(), now(), now());
--1|Date|Date|Date|2 <--using my car_code_sequence
Unfortunately, when i invoke a "create" operation in a "car_controller the rails application generate this statement:
INSERT INTO "cars" ("created_at", "car_code", "car_date", "updated_at")
VALUES ($1, $2, $3, $4) RETURNING "id" [
["created_at", Mon, 04 Mar 2013 14:39:55 UTC +00:00],
["car_code", nil],
["car_date", Mon, 04 Mar 2013 14:39:55 UTC +00:00],
["updated_at", Mon, 04 Mar 2013 14:39:55 UTC +00:00]]
So, my question is:
Who can I change the Car Model to exclude the column "car_code" from insert statement (but keeping the "car_code" in database), i.e., to have the same behaviour as "id").

Answer 1

Try to add this code at car model:
class Car < ActiveRecord::Base
## --------------------- Ignore columns patch ------
##ignore_column_pattern = /^car_code/
class << self
alias :all_columns :columns
def columns
#columns_filt ||= all_columns.reject { |col| col.name =~ ##ignore_column_pattern }
end
end
alias :all_attribute_names :attribute_names
def attribute_names
#attr_names_filt ||= all_attribute_names.reject { |att| att =~ ##ignore_column_pattern }
end
## ------------------- / Ignore columns patch ------
end
From: https://stackoverflow.com/a/10319903/1042324