ArrayAppend() Does Not Work With ColdFusion's XML Pseudo-Node-Sets

Posted December 22, 2008 at 9:27 AM

Tags: ColdFusion

I stumbled upon this the other day; at first, I was a bit confused, but the more I think about it, the more I understand that it makes perfect sense. ColdFusion's ArrayAppend() method works with XML children, but not with pseudo-XML-node-sets. Take a look at this example:

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  • <!--- Define our ColdFusion XML document. --->
  • <cfxml variable="xmlData">
  •  
  • <girls>
  • <girl name="Kimmie" />
  • <girl name="Kit" />
  • <girl name="Sarah" />
  • <girl name="Jill" />
  • </girls>
  •  
  • </cfxml>
  •  
  • <!---
  • Append a duplicate girl node to the list of girl nodes.
  • By duplicating, the parent document should be handled
  • automatically.
  • --->
  • <cfset ArrayAppend(
  • xmlData.girls.girl,
  • Duplicate( xmlData.girls.girl[ 1 ] )
  • ) />
  •  
  • <!--- Dump out the new XML document. --->
  • <cfdump
  • var="#xmlData#"
  • label="xmlData After Duplicate() Append."
  • />

Here's we're just duplicating an XML node and then appending it onto the originating node list. When we run this code, we get the following ColdFusion error:

The ArrayAppend ColdFusion function is not supported on this object. The ArrayAppend ColdFusion function is not supported on an object of type coldfusion.xml.XmlNodeListWrapper. For example, XML objects can be operated on by a subset of the structure and array functions, but not all.

The problem here is that we are not using the XmlChildren collection. Rather, we are using the pseudo-node-set:

xmlData.girls.girl

What this does is collect all of the "girl" nodes into a coldfusion.xml.XmlNodeListWrapper object to allow for easier (and perhaps more meaningful) traversal. And, in an example like the one above, it might seem silly since the girl pseudo-node-set is the same as the collection of all XmlChildren nodes. However, remember that if we have mixed nodes, the pseudo-node-set will still work.

The simple fix for this is to refer to the child nodes using the XmlChildren collection:

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  • <cfset ArrayAppend(
  • xmlData.girls.XmlChildren,
  • Duplicate( xmlData.girls.girl[ 1 ] )
  • ) />

This time, the code runs as expected.

So, this is a minor note; but, if you don't realize what is going on, it could really trip you up - perhaps even make you believe that you can't append XML nodes to an existing document.

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