## orders_controller.rb (snippet)
  def new
    @user = current_user
    @order = Order.new(:user_id => @user.id, :order_status => "initial", 
                       :checkout_at => Time.now, :apples => ???)
    @order.save    
  end

### order.rb
class Order < ActiveRecord::Base
 
  attr_accessor :apples

  has_and_belongs_to_many :line_items
  belongs_to :user
  
  validates_numericality_of :user_id
  after_create :create_line_items

  
  def create_line_items
    apples.each do |a|
      item = LineItem.new(:inventory_id => a.id,
                          :price_plan_id => a.price_plan_id,
                          :qty => a.quantity,
                          :customer_price => a.price)
      self.line_items << item
    end
  end
    
  def total_price
    LineItem.sum(:customer_price, :conditions => ["order_id = ?", self])
  end
  
en