## Order class
class Order < ActiveRecord::Base
  has_many :productorders do
    def get_amount_by_product_id(product_id)
      po = Productorders.find_by_order_id(self).find_by_product_id(product_id)
      if po.nil?
        return 0
      else
        return po.amount
      end
    end
  end
  has_many :products, :through=>:productorders
  belongs_to :customer
end

## Productorder is the join table of order and product

class Productorder < ActiveRecord::Base
  belongs_to :product
  belongs_to :order
end

## Migration of productorder
class CreateProductorders < ActiveRecord::Migration
  def self.up
    create_table :productorders, :id=>false do |t|
      t.integer :amount
      t.integer :product_id
      t.integer :order_id

      t.timestamps
    end
  end

  def self.down
    drop_table :productorders
  end
end


## Product class
class Product < ActiveRecord::Base
  has_many :productorders
  has_many :orders, :through => :productorders
end