I do how in book, add method:
def clear_cart
    @cart = get_cart
    @cart.[u]initializeinitialize</u>
end

and add method:
def clear
    @purchases = []
    @price = 0.0
end

connecting to action clear_cart - error:
  NoMethodError in BuyController#clear_cart
  undefined method `initializeinitialize' for #<Cart:0x4737374>
  ..
  ..
  Response
  Headers: {"cookie"=>[], "Cache-Control"=>"no-cache"}

what is initializeinitialize?

read the Errata

http://www.wrox.com/WileyCDA/WroxTit...ew_errata.html

Also make sure that you download the code. that will help you as well.. theres a lot of typos that aren't cought in errata

cazalot, thank you