[flexcoders] expected behaviour? (e4x)

[nwebb]

Hi,

Could someone run this code and let me know whether it is expected
behaviour?

The snippet of code (below) is looking for xml nodes which match a certain
criteria - it then pops them in an XMLListCollection.
I have no problem finding the nodes and populating the collection. However,
on the second time around I noticed that my original XML data gets modified
as well. I figured that this must be a reference problem, and it does appear
to be (see comments in code for solution), but I wouldn't expect to need to
do this here, as I'm only reading the data, not writing to it or anything
that references it.


Below is a the code for the mxml file:
1) Run it in debug mode
2) Choose "Brazil" from the ComboBox
3) Step through it and watch the original xml data (myTestData) change when
the second match is added to the XMLListCollection.

Any understanding of this would be appreciated

******* Here is the code: ********


<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"; layout="absolute"
    verticalScrollPolicy="off" horizontalScrollPolicy="off"
    paddingBottom="5" paddingLeft="5" paddingRight="5" paddingTop="5"
height="399" width="514">
    <mx:Script>
        <![CDATA[
            import mx.collections.XMLListCollection;
            import mx.controls.ComboBox;
            import mx.collections.ArrayCollection;
            import mx.events.ListEvent;
            import mx.events.TreeEvent;

            [Bindable] private var countries:Array =
["all","Brazil","Colombia", "Peru"];
            [Bindable] private var description:String = "";

            private var myTestData:XML =
                    <tree>
                        <node>
                            <label>AAA</label>
                            <country>Kenya</country>
                        </node>
                        <node>
                            <label>BBB</label>
                            <country>Brazil</country>
                        </node>
                        <node>
                            <label>CCC</label>
                            <country>Brazil</country>
                        </node>
                        <node>
                            <label>DDD</label>
                            <country>Peru</country>
                        </node>
                    </tree>;

            private function onCountryComboChange(event:ListEvent):void
            {
                var countryString : String = ComboBox(event.currentTarget
).selectedItem.toString();
                var nodesMatchingQuery : XMLListCollection = new
XMLListCollection();

                var CHECKMYORIGDATA = myTestData;

                if(countryString != "all")
                {
                   //SOLUTION IS TO  LOOP THROUGH myTestData..node.copy() -
BUT
                   //WHY SHOULD I NEED TO LOOP THROUGH A COPY WHEN I'M ONLY
READING THE DATA?
                   for each(var theNode:XML in myTestData..node)
                    {
                        var keywords:XMLList = theNode.country;
                        var numMatches:uint =
keywords.(text()==countryString).length();
                        if(numMatches >= 1){
                            //STEP THROUGH THIS CODE, LOOKING AT THE
ORIGINAL XML
                            nodesMatchingQuery.addItem(theNode); //THIS
ALTERS myTestData ON SECOND ATTEMPT
                        }
                    }
                }
            }
        ]]>
    </mx:Script>
    <mx:VBox height="100%">
            <mx:ComboBox width="141" dataProvider="{countries}"
change="onCountryComboChange(event)"/>
        </mx:VBox>
</mx:Application>