Introduction to XML in Flash
       by senocular

Nested Loops
Simple collections of data in XML is fairly easily traversed. So far we've covered to basic ways to do this. One was the more common for loop going through a childNodes array and the other a do..while loop that cycled through siblings. The structure of an XML document is not always as simple as that in the squirrel finder, though. Often you could be dealing with nested collections of elements within other nested collections of other elements. Not only would you have to loop through one collection, but possibly each collection within that collection. For this, you would need to use nested looping.

Just like XML elements can be nested, you too can nest your loops in Flash to facilitate this added complication in an XML document's structure. Depending on how deep your XML goes may decide just how much looping you'll need to do and how many you'll need to nest. For example, take the following:

<pirate name="Black Beard">
<saying phrase="Argh!" />
<saying phrase="Shiver me timbers" />
<pirate name="Francis Drake">
<saying phrase="Avast!" />
<saying phrase="Polly want a cracker?" />
<saying phrase="Well blow me down" />

Here we're dealing with 2 element sets that run 2 levels deep; pirates and sayings within individual pirates. Understand that these sayings are not historically accurate. I'm pretty sure Black Beard said "Avast!" just as much as the next guy. Either way, in order to get all the sayings of all the pirates, you would need to first loop through each pirate, then, while on each, loop through their sayings - a loop within a loop. You can potentially have many nested loops, but the fewer the better. Here is a quick code snippet of what you might use to loop through the above pirates XML:

var pirates = pirates_xml.firstChild.childNodes;
for (var p=0; p<pirates.length; p++){
var pirate = pirates[p];
var sayings = pirate.firstChild.childNodes;
for (var s=0; s<sayings.length; s++){
var saying = sayings[s];
trace( +" says \""+ saying.attributes.phrase +"\"");

This would output the following in Flash:

Black Beard says "Argh!"
Black Beard says "Shiver me timbers"
Francis Drake says "Avast!"
Francis Drake says "Polly want a cracker?"
Francis Drake says "Well blow me down"

Of course should you need to implement nested for loops, you probably won't just be tracing the information. More than likely you'll be converting it into a more usable and ActionScript-centric form that works better with the setup of your movie. How that is done depends on your movie.


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