Flex Newbie XMLList question - Sorting XML and XMLList

Question

Is it possible to sort an XMLList? All the examples I can find on it create a new XMLListCollection like this:

MyXMLListCol = new XMLListCollection(MyXMLList);

I don't think the XMLListCollection in this case has any reference to the XMLList so sorting it would leave my XMLList unsorted, is this correct?

How can I sort the XMLList directly?

Thanks ~Mike

Answer 1

While there is no native equivalent to the Array.sortOn function, it is trivial enough to implement your own sorting algorithm:

// Bubble sort.

// always initialize variables -- it save memory.
var ordered:Boolean = false;
var l:int = xmlList.length();
var i:int = 0;
var curr:XML = null;
var plus:XML = null;
while( !ordered )
{
 // Assume that the order is correct
 ordered = true;
 for( i = 0; i < l; i++ )
 {
  curr = xmlList[ i ];
  plus = xmlList[ i + 1 ]; 

  // If the order is incorrect, swap and set ordered to false.
  if( Number( curr.@order ) < Number( plus.@order ) )
  {
   xmlList[ i ]   = plus;
   xmlList[ i + 1 ] = curr;
   ordered = false;
  }
 }
}

but, realistically, it is far easier and less buggy to use XMLListCollection. Further, if someone else is reading your code, they will find it easier to understand. Please do yourself a favor and avoid re-inventing the wheel on this.

Answer 2

So I finally got my search terms altered enough I actually churned up an answer to this. Using the technique I got from here: http://freerpad.blogspot.com/2007/07/more-hierarchical-sorting-e4x-xml-for.html

I was able to come up with this:

public function sortXMLListByAttribute(parentNode:XML,xList:XMLList,attr:String):void{
//attr values must be ints
var xListItems:int = xList.length();
if(xListItems !=0){
 var sortingArray:Array = new Array();
 var sortAttr:Number = new Number();
 for each (var item:XML in xList){
  sortAttr = Number(item.attribute(attr));
  if(sortingArray.indexOf(sortAttr)==-1){
   sortingArray.push(sortAttr);
  }
  //piggy back the removal, just have to remove all of one localName without touching items of other localNames
  delete parentNode.child(item.localName())[0];
 }
 if( sortingArray.length > 1 ) {
  sortingArray.sort(Array.NUMERIC);
 }

 var sortedList:XMLList = new XMLList();
 for each(var sortedAttr:Number in sortingArray){
  for each (var item2:XML in xList){
   var tempVar:Number = Number(item2.attribute(attr));
   if(tempVar == sortedAttr){
    sortedList += item2
   }
  }
 }
 for each(var item3:XML in sortedList){
  parentNode.appendChild(item3);
 }
}
}

Works pretty fast and keeps my original XML variable updated. I know I may be reinventing the wheel just to not use an XMLListCollection, but I think the ability to sort XML and XMLLists can be pretty important