ColdFusion Doesn't Need NULLs

I recently read Joe Rinehart's great blog on OO features in ColdFusion. His blog is, largely, a response to some discussions on the CFCDev list. In short, he feels that many of the OO features that some people are requesting be added to ColdFusion aren't a good idea.

The argument that I found the most interesting (on Joe's blog and the CFCDev list) was regarding NULLs.

The Problem

He defines the problem better than I can (reading his post first if you have time). Essentially, the problem is that having a returntype (say "numeric") for a method is helpful. With that help, however, comes a challenge. It isn't possible to return no value. With a returntype of "string", you could return an empty string. With a returntype such as "numeric", however, returning zero isn't the same. In fact, an empty string might not be the same as no value either.

Many (typed) languages (including SQL) handle this with a NULL. Basically, a NULL is an indication of no value at all.

The argument made by many is that NULL is needed so that we can take advantage of returntype and still return no value from a method.

My Proposal

I have run into this issue myself. Of course, adding a NULL to ColdFusion (or any typeless language) seems like a pretty major change.

As it happens, ColdFusion already has its own conception of this. A variable can be undefined (that is non-existent). A component with a returntype of "any" or "void" need not execute a cfreturn (and thereby return a value).

I would like an optional attribute (maybe "allowVoid"), which would allow a method with any other returntype to not execute a cfreturn. The attribute would have to default to false in order to maintain backward compatibility.

It is already possible to have the following code leave "foo" undefined (if myMethod doesn't execute a cfreturn). This change would only mean that myMethod could have a returntype of something other than "any" or "void" (if allowVoid is set to "true").

<cfset foo = comp.myMethod()>

This nice thing about this approach is that it plays nicely with how things work in ColdFusion already. It doesn't add a concept of NULL, which is foreign to ColdFusion. It does, however, add the ability to return nothing from a component without giving up the type-checking benefits of returntype.

I might also add that the problem already doesn't exist in cfargument as you can already set required="false" in cfargument.

Well, there you have it. If you have any thoughts on my proposal, I would love to hear them. If you have any thoughts on other OO features or anything else discussed in Joe's blog, please post them there to keep that discussion coherent.