This was really useful and we successfully implemented this approach (using `onBeforeAddressUpdate` and `onBeforeAddressCreate` to capture the country and postcode on form submit, to apply country specific postcode validation). We were using legacy checkout and used `JError::raiseWarning` to return an error to the user if the postcode didn’t pass validation. All worked well.
We are now in the process of moving away from the legacy checkout to the newer code, and are struggling to output our custom postcode validation error messages.
Looking at the documentation we can't see a way to do this in the address API. However, the shipping API (for example) looks like it has a `$messages` variable available to send info back. Is there something like this for the address API which we have somehow missed?
FYI we are currently using Hikashop 3.2 Business Edition, but are looking to upgrade to 3.4 soon.
Thanks again.