How to enforce uniqueness of column on nested attributes:

Question

Lets say I had the following setup

class User < ActiveRecord::Base
    has_many :address
    accepts_nested_attributes_for :address, allow_destroy: true
end

class Address < ActiveRecord::Base
    attr_accessible :house_color, :street_address
end

And for some reason, I wanted to only allow a given user to have one address of a given color.

How would I lock down? something like

   validates :address.house_color.unique

Except functional....

Thanks!

Answer 1

class User < ActiveRecord::Base
  has_many :address
  accepts_nested_attributes_for :address, allow_destroy: true
  validates_associated :addresses
end

class Address < ActiveRecord::Base
  belongs_to :user
  attr_accessible :house_color, street_address
  validates_uniqueness_of :house_color. :scope => :user_id
end

Answer 2

Another way would be to use reject_if

accepts_nested_attributes_for :address, allow_destroy: true, reject_if: proc { |attributes| Address.where(:house_color => attributes["house_color"], :user_id => attributes["users_id]).exists? }