I am using ColdFusion 9.0.1
I recently read that in ColdFusion 9, it is now advised to use isNull() and not use isDefined().
I didn't find much info on this at all around the web.
Is there any advantage to using one or the other in ColdFusion 9?
I know that in general people have been moving away from it for some time. The main use for it was to determine whether a variable existed in a particular scope, but structKeyExists() is more precise for that. IsDefined() works very hard to find any possible instance of the variable you've asked for. (Sean Corfield had a bit to say about structKeyExists vs. isDefined.)
I've not seen anywhere a recommendation to use isNull() instead of isDefined. Actually, I would have expected isNull to return an error if you give it an undefined variable, but apparently that works.
How do you do dynamic variables, though?
structKeyExists(form,"address_" & i)
You can try array notation...
isNull(form["address_" & i])
...but if i is undefined this throws an error.