Agile Web Development with Rails - Chapter 8, Task C, Error

Kenny Mr wrote:

I am currently in Chapter 8, Task C, Cart Creations. On pages 110 and
111, it shows modifications needed to be made to the following files:

app/controllers/store_controller.rb
app/views/store/add_to_cart.rhtml
app/models/cart.rb

When I make the changes and refresh my browser, I get an error message,
"No method error in store#add_to_cart". I have defined the total_price
method in my cart.rb file, so I fail to see where the error about there
not being a method entitled total_price comes up at. Has anyone else
had this trouble?

Help is appreciated.

If you read further down 111 you will see that he shows that error to
be expected. He then shows you the importance of paying attention to
session data. To clear the error you are to run:
rake db:session:clear

typo, should be sessions not session:
rake db:sessions:clear