Answer by sethvargo for Rails 3 - Nested Resources - Routing

you should be using orer_products_path (not url). If you go to the root of your app and type,

rake routes

that will give you a list of all named routes. You need to append _path to them though (returns the string representation). This is a handy little trick for figuring out named routes.

Now to your real question - of course it doesn't exist! You just deleted it! You are destroying the product instead of the product from the order!