Do you mind elaborating? I can see how the user's ability to 'place-order' might be rejected between the access check and the order creation but that would be an extraordinary edge-case that does not need to be accounted for in 99% of applications.
If you're developing an application that needs to account for such an edge case you could easily do so with an insert w/ join method on the Order model. The author isn't trying to show that the code is bulletproof for every scenario.
If you're developing an application that needs to account for such an edge case you could easily do so with an insert w/ join method on the Order model. The author isn't trying to show that the code is bulletproof for every scenario.