nested_attributes

gistfile1.rb

class Product < ActiveRecord::Base
  has_many :fields, :as => :attributable, :dependent => :destroy
  accepts_nested_attributes_for :fields
end

class Field < ActiveRecord::Base
  belongs_to :attributable, :polymorphic => true
  belongs_to :column
  
  scope :with_column, select("fields.*, columns.column_name AS 'name'").joins(:column)
  
  validates_presence_of :column_id, :value
end

class Variant < ActiveRecord::Base
  belongs_to :store
  belongs_to :product
  has_many   :supply_movements, :dependent => :delete_all
  has_many   :sale_items
  has_many   :order_items
  has_many :fields, :as => :attributable 

  accepts_nested_attributes_for :fields, :reject_if => lambda { |a| a.values.all?(&:blank?) }

  # validates_presence_of :product
  validates_inclusion_of :active, :in => [true, false]
  
  attr_accessible :store_id, :price, :reference, :barcode, :minimum_stock, :stock, :fields_attributes
end