class Delivery < ActiveRecord::Base belongs_to :supplier has_one :invoice has_many :stock_changes, :dependent => :destroy scope :recent, :order => 'created_at DESC', :limit => 10 validates_presence_of :supplier_id accepts_nested_attributes_for :stock_changes, :allow_destroy => :true def new_stock_changes=(stock_change_attributes) for attributes in stock_change_attributes stock_changes.build(attributes) unless attributes[:quantity].to_i == 0 end end end