app/models/event_order_fulfillment.rb
class EventOrderFulfillment < ActiveRecord::Base
belongs_to :order, class_name: 'EventOrder'
validates :tracking_number, presence: true
validates :tracking_number, length: { is: 12 }, allow_blank: true
after_create do
OrderFulfillmentMailer.delay.notify_user_fulfilled(self)
OrderFulfillmentMailer.delay.notify_organizer_fulfilled(self)
end
end