Question

I have a model Competitor like this

class Competitor < ActiveRecord::Base
  belongs_to :admin_user
  has_many :companies
  attr_accessible :admin_user_id, :c1, :c2, :c3, :c4, :c5
  validates :admin_user_id, :presence => true
  validates_uniqueness_of :admin_user_id, :message => "This user has yet a competitors list"

end

C1, c2,.. are the id of companies. Selected from a drop down list. How can I validate the uniqueness of a row?
(i.e. is not possible to have two or more equals companies for an admin user BUT they can be empties).

Answer 1

You could write your own validation method that would enforce this.

class Competitor < ActiveRecord::Base
  belongs_to :admin_user
  has_many :companies
  attr_accessible :admin_user_id, :c1, :c2, :c3, :c4, :c5
  validates :admin_user_id, :presence => true
  validates_uniqueness_of :admin_user_id, :message => "This user has yet a competitors list"

  validate :check_companies

  def check_companies
    #[do your checks]
  end

end