ajaxCFC and 0 Return Values

I've been using ajaxCFC on a project at work and I ran into an issue today which I thought I'd share.

Say you have a simple ajax component:

<cfcomponent extends="ajax">   
   <cffunction name="echo" output="no" access="private">
      <cfargument name="num" required="yes" type="numeric">      
      <cfreturn val(arguments.num) />

You set up a call to this method like so:

   <title>echo number example</title>
   <script type='text/javascript'>
      _ajaxConfig = {   '_cfscriptLocation':'echoNumber.cfc',
   <script type='text/javascript' src='../js/ajax.js'></script>
   <script type="text/javascript">
      function doEcho()   {
         DWREngine._execute(_ajaxConfig._cfscriptLocation, null, 'echo', 0, doEchoResult);

      // call back function       function doEchoResult (r) {

<body onload="doEcho();">
   <p>Nothing Happens!</p>

This results in the following response:

HTTP/1.1 200 OK
Connection: close
Date: Wed, 07 Mar 2007 18:14:36 GMT
Server: Microsoft-IIS/6.0
Content-Type: text/html; charset=UTF-8

_3952_1173291282046 = 0;

DWREngine._handleResponse('3952_1173291282046', _3952_1173291282046);

This looks fine, however the callback function doEchoResult never gets called. The reason is the DWREngine._handleRespone function checks the result before calling the callback function.

DWREngine._handleResponse = function(id, reply) {
if (handlers && reply) {
try {
if (handlers.callback) handlers.callback(reply);
catch (ex) {
DWREngine._handleMetaDataError(handlers, ex);

The problem here is that the reply argument (the _3952_1173291282046 variable in this example) will be evaluated to false so the callback never gets called.

Now the DWREngine code could be updated to handle this by checking that reply != null, however I'm a little leary of changing core framework code. Plus I haven't really taken a good look at the DWREngine code to know if this will cause any other issues. In the end I decided to modify my component function to work around this issue rather than change the core ajaxCFC files. I've submitted a bug to the RIAForge project, so this may get fixed in a future release. (Or maybe Rob Gonda will chime in and tell me I'm doing things all wrong. :)

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# Posted By dave | 9/17/08 5:49 AM
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