model won't create because can't find ID in Rails

I have two models.

class User 
  has_one  :spec, :dependent => :destroy

    # returns true for a duplicat record
       def duplicate?
         user = User.find_by_email(email)
         self.id = user.id unless user.nil?  
         not user.nil?
       end


  class Spec
  belongs_to :user

  validate_uniqueness_of :user_id

Controller

if @user.duplicate? || @user.save

 @user.create_spec(:birthdate => params[:user][:deliver_on])

end

This produces the following error:

ActiveRecord::StatementInvalid in BoardController#new

Mysql::Error: Column 'user_id' cannot be null: INSERT INTO `specs` (`created_at`, `birthdate`, `updated_at`, `avatar`, `gender`, `user_id`, `last_name`, `first_name`, `picture`) VALUES('2011-03-09 05:43:46', NULL, '2011-03-09 05:43:46', '../images/default_avatar.jpg', NULL, NULL, '', '', NULL)

However if I do this:

@user.create_spec(:user_i开发者_StackOverflowd => @user, :birthdate => params[:user][:deliver_on])

it works!

I thought doing @user.create_spec would supplies the user_id automatically.

Anyway to make this work the way its supposed to? I appreciate any feedback. Thank

---

I think you are having the wrong approach. According to you,

class User 
  has_one :spec
end

But you are creating another spec for duplicate user. So I suggest following link.

http://www.hackerdude.com/2005/11/28/one-to-one-relationships-with-rails/