Overriding returnFormat at runtime

Ok, so this falls in the "Not so sure this is a good idea" department. Stefan Vesterlund posted a comment on my last blog entry concerning returnformat. He asked if it was possible to change the returnFormat at runtime. I said that I didn't think it was possible, but that you could simply use returnFormat="plain" and return JSON or WDDX manually. He played around with it and discovered you could override the default behavior. Consider the following code sample.

<cffunction name="testMethod" access="remote">
   <cfset var a = [1,2,4,9]>
   <cfreturn a>
</cffunction>

Since I've specified no returnFormat in the cffunction tag, if I hit this via the browser and don't override returnFormat in the query string, the result will be a WDDX string. Now consider this version:

<cffunction name="testMethod" access="remote">
   <cfset var a = [1,2,4,9]>
   <cfif a[1] is 1>
      <cfset url.returnFormat="json">
   </cfif>
   <cfreturn a>
</cffunction>

The code now checks the first entry in the array, and if the value is 1, it sets url.returnFormat. Surprisingly this works. I guess ColdFusion doesn't bother worrying about the returnFormat settings until the end of the method, which kinda makes sense.

I still feel weird about this one, but thought I'd pass it along.

Comments (3) Jul 3, 2008 8:20 AM Views: 1127

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I could see this as maybe being useful in the sense that you could have a single multiple use function.

--Dave
# Posted By Dave Ferguson | 7/3/08 8:42 AM
Well, my issue is that CF already provides a way to override the returnFormat. The client does it (using the query string). This though is all server side.

I don't know - it just feels wrong. :)
# Posted By Raymond Camden | 7/3/08 8:47 AM
This could be used to make sure the return format isn't altered. (Not that I see a use case issue, but that would be one scenario.)
# Posted By John Farrar | 7/3/08 4:42 PM
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