shipment_decorator.rb

Spree::Shipment.class_eval do
  scope :exportable, -> { joins(:order).where('spree_shipments.state != ?', 'pending') }

  def self.between(from, to)
    joins(:order).where('(spree_shipments.updated_at > ? AND spree_shipments.updated_at < ?) OR (spree_orders.updated_at > ? AND spree_orders.updated_at < ?)',from, to, from, to)
  end

private
  def send_shipped_email
    Spree::ShipmentMailer.shipped_email(self).deliver if Spree::Config.send_shipped_email
  end
end