Finding nodes with a namespaced attribute using e4x

12.19.2009

When digging through XML, e4x is definitely your friend but it can be tricky sometimes. I recently came across a situation where I needed to find all nodes with a certain namespaced attribute. I didn’t care what the attribute’s value was; I just needed to know which nodes had the attribute.

Take the following XML:

<catalog xmlns:ah="http://aaronhardy.com/music">
	<cd>
		<title>Empire Burlesque</title>
		<artist ah:verified="false">Bob Dylan</artist>
		<country>USA</country>
		<company>Columbia</company>
		<price>10.90</price>
		<year>1985</year>
	</cd>
	<cd>
		<title>Hide your heart</title>
		<artist>Bonnie Tyler</artist>
		<country>UK</country>
		<company>CBS Records</company>
		<price>9.90</price>
		<year>1988</year>
	</cd>
	<cd>
		<title ah:verified="true">Greatest Hits</title>
		<artist>Dolly Parton</artist>
		<country>USA</country>
		<company>RCA</company>
		<price>9.90</price>
		<year>1982</year>
	</cd>
	<cd ah:verified="false">
		<title ah:verified="true">Still got the blues</title>
		<artist>Gary Moore</artist>
		<country>UK</country>
		<company>Virgin records</company>
		<price>10.20</price>
		<year>1990</year>
	</cd>
	<cd>
		<title>Eros</title>
		<artist>Eros Ramazzotti</artist>
		<country ah:verified="false">EU</country>
		<company>BMG</company>
		<price>9.90</price>
		<year>1997</year>
	</cd>
</catalog>

In this case I’m trying to find all nodes that have a “verified” attribute. Again, I don’t care if the attribute’s value is true or false. If the attribute weren’t in the “ah” namespace I would use this line of code:

var nodes:XMLList = myXML..*.(hasOwnProperty('@verified'));

However, since the attribute is in the “ah” namespace, the query takes this form:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" creationComplete="cc()">
	<mx:Script>
		<![CDATA[
			protected function cc():void
			{
				var myXML:XML = 
					<catalog xmlns:ah="http://aaronhardy.com/music">
						<cd>
							<title>Empire Burlesque</title>
							<artist ah:verified="false">Bob Dylan</artist>
							<country>USA</country>
							<company>Columbia</company>
							<price>10.90</price>
							<year>1985</year>
						</cd>
						<cd>
							<title>Hide your heart</title>
							<artist>Bonnie Tyler</artist>
							<country>UK</country>
							<company>CBS Records</company>
							<price>9.90</price>
							<year>1988</year>
						</cd>
						<cd>
							<title ah:verified="true">Greatest Hits</title>
							<artist>Dolly Parton</artist>
							<country>USA</country>
							<company>RCA</company>
							<price>9.90</price>
							<year>1982</year>
						</cd>
						<cd ah:verified="false">
							<title ah:verified="true">Still got the blues</title>
							<artist>Gary Moore</artist>
							<country>UK</country>
							<company>Virgin records</company>
							<price>10.20</price>
							<year>1990</year>
						</cd>
						<cd>
							<title>Eros</title>
							<artist>Eros Ramazzotti</artist>
							<country ah:verified="false">EU</country>
							<company>BMG</company>
							<price>9.90</price>
							<year>1997</year>
						</cd>
					</catalog>;
 
				var ns_ah:Namespace = new Namespace('http://aaronhardy.com/music');
				var verified:QName = new QName(ns_ah, '@verified');
				var nodes:XMLList = myXML..*.(hasOwnProperty(verified));
				trace(nodes.toXMLString());
			}
		]]>
	</mx:Script>
</mx:Application>

Hope that helps someone!

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