E4X in ActionScript 3 and Flex 3

The following top AS3 classes, in conjunction with HTTPService and mx.rpc.events.ResultEvent classes are used in Flex (2+) to handle XML:


XMLList Class can be considered a collection of XML objects. It is a native ActionScript class that is advised to handle XML such as data binding. XMLNode has become the legacy class in AS 2.

So the first step of handling XML data is to deserialize an XML document or object into XMLList objects.

<mx:HTTPService id="dataFetcher" url="http://mysite/myData.xml" resultFormat="e4x" result="onData(event)" />

Remember you will almost always need to initialize the call by adding the following code to the “creationComplete” event handler of the mx:Application node:

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" creationComplete="dataFetcher.send()"/>

To deserialize the an XML object (sample shown as follows), use ResultEvent Class, like so:

<delSum Test="1" timestamp="2007-12-10T21:07:48Z">
<del pId="Dem" dNeed="2029" dTot="4056" dChosen="991" dToBeChosen="3237">
<Cand cId="1746" cName="Clinton" dTot="290" d1="+290" d7="+290" d30="+150"/>
<Cand cId="1918" cName="Obama" dTot="194" d1="+194" d7="+194" d30="+55"/>
<del pId="GOP" dNeed="1113" dTot="2225" dChosen="251" dToBeChosen="2153">
<Cand cId="893" cName="Romney" dTot="109" d1="+109" d7="+109" d30="+1"/>
<Cand cId="302" cName="Paul" dTot="47" d1="+47" d7="+47" d30="0"/>

private function onData(event:ResultEvent):void
demData = event.result.del.(@pId=="Dem").Cand.(@cName!="Uncommitted");
gopData = event.result.del.(@pId=="GOP").Cand.(@cName!="Uncommitted");

Note that event.result represents the top node, which is <delSum> node in the XML document.

XML filtering:

To locate a set of XML objects that represents similar characteristics, use the parenthesis () to include sets of boolean statements, following a dot after the node you want to carry out the filtering against, like so:

var product1:XMLList = catalog.product.(@id==1);//Returning the product node or nodes if there are multiple products whose id is equal to 1


var productName:String = catalog.product.(price<50).name;//Returns the name node


var manufName:String = catalog.product.(price<50).@manufacturer;//Returns the manufacturer attribute under the name node

To get list of candidate names:

var _tst:XMLList = event.result.del.(@pId=="GOP").Cand.(@cName!="Uncommitted").@cName
trace((_tst[0] is XML)+"; "+_tst[0].nodeKind() )//Returns "true; attribute"
trace(gopData[0].@cName+"; "+(gopData[0].nodeKind())//Returns "Romney; element"

Types of node include: text, comment, processing-instruction, attribute, or element.


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