undefined method `line_items' for nil:NilClass when clicking checkout Ch 12

Following tutorial w/ rails 4.0.beta and ruby 2.0. In the chapter 12 checkout section when I click checkout I get the below error instead of figure 22 on page 166. Have others experienced this? If so send a solution. Thanks.

NoMethodError in OrdersController#new

undefined method `line_items’ for nil:NilClass

error points to this line in the orders controller

if @cart.line_items.empty?

This is an error in the current printing of the book, and will be fixed in the next printing.

The error messages you are getting indicates that @cart has a value of nil, as that is the object to which you are sending the line_items method.

To correct this, add the following lines at the top of the file:

include CurrentCart
before_action :set_cart, only: [:new, :create]

You can see what the result looks like at the following URL:

http://media.pragprog.com/titles/rails4/code/ra…