order_module.rb

#route.rb
  map.resources "orders", order_hash do |order|
    order.resource "invoice"
    order.resource "payment", :new => {"express" => :get}
  end
  #map.resoures "payments" # not in use anymore !

#payments_controller.rb
  before_filter :require_order
  def show
    @payment = @order.payment
  end

#order_module.rb
module OrderModule #included in application_controller
  def require_order
    unless find_and_set_current_order
      flash[:notice]= "INVALID URL : the order you were trying to reach doesn't belong to your account"
      redirect_to "/account"
      return false
    end
  end

  def find_order
    @order = current_user.orders.find_by_id(params[:order_id] || params[:id])
  end

  def set_current_order
    @order && ( self.current_order==@order || self.current_cart= (self.current_order= @order).assets )
  end

  def find_and_set_current_order
    find_order && set_current_order
  end
end