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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 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.