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Calling a function... did you really call it?

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Posted in ColdFusion | Posted on 06-25-2009 | 2,908 views

Just ran across an interesting bug in some code I'm reviewing. I've done this myself a few times so I certainly don't blame the original developer. Read this real quick and tell me what the output is:

view plain print about
1<cffunction name="returnNothing" output="false" returnType="string" hint="Ask Paris Hilton about WW2.">
2    <cfreturn "">
3</cffunction>
4
5<cfif len(returnNothing)>
6    Yes, this ran, and it never should!
7<cfelse>
8    Perfect - I got nothing back. As I expected.
9</cfif>

If you said "Perfect...", then you are incorrect. Notice the cfif. We called the UDF, and it should have returned a blank string, right? Well, we didn't actually call the UDF. See the missing ()?

So why did len() return true? You can see this for yourself. Running:

view plain print about
1<cfoutput>#returnNothing#</cfoutput>

outputs:

cftest22ecfm1623321220$funcRETURNNOTHING@76e45ffe

Which I believe is simply a toString version of the UDF. (Actually I compared it to #toString(returnNothing)# and I got the same thing.)

So - raise your hand if you've made this mistake as well!

Comments

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Jonathan said on 06-25-2009 at 1:07 PM #
actually, I haven't! I have just made every other mistake in the book besides this one
Adam Ness said on 06-25-2009 at 1:15 PM #
Yeah, the fact that functions are objects in ColdFusion is the source of many little errors that I've made over the years. Sometimes very subtle ones too...

I wonder what the same code returns in Railo though..
TJ Downes said on 06-25-2009 at 1:30 PM #
I'm sure I have made the same mistake in the past, but it was refreshing to know I spotted the error first time reading the code :)
Damon Gentry said on 06-25-2009 at 1:48 PM #
I, for one, have never made that mistake. And for the record, "I'm shocked, shocked to find that gambling is going on in here!"
Jose Galdamez said on 06-25-2009 at 2:01 PM #
I'll admit I've done this before, but probably more so in JavaScript than in CF.
Brian Swartzfager said on 06-25-2009 at 2:37 PM #
I was just muttering to myself the other day that I have to stop forgetting to leave the "()" off the end of my Transfer function calls ("user.getFirstName" instead of "user.getLastName()"). :)

I think it's because in my mind I associate those ORM functions with the query-based variables I still use when looping through query results.
Raymond Camden said on 06-25-2009 at 2:38 PM #
The code in question actually _was_ a Transfer-based call.
Sean in CT said on 06-25-2009 at 2:47 PM #
Interesting - would never have thought to do it that way to begin with. Great question/example!
Tom McNeer said on 06-25-2009 at 3:13 PM #
Transfer calls are where I always make that mistake, too, especially when chaining composed objects:

<cfreturn user.getRole().getRoleName() and such.

It's really easy to leave one out in the middle somewhere.
Nathan Kondra said on 06-26-2009 at 1:36 PM #
Oh most certainly. Back in the day I don't think there was a ColdFusion mistake that I have written.

This also reminds me of another issue I found just recently while reviewing someone code. Going to use the same example above to illustrate.

<cfif len("returnNothing")>
Yes, this ran, and it never should!
<cfelse>
Perfect - I got nothing back. As I expected.
</cfif>
Frank said on 06-30-2009 at 6:52 AM #
Nope. Never done that.

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