Flex error 1034: Type Coercion Failed

Question

I extended the File class as AudioFile.  I only added one new property "category".  I intend to filter files out of a directory structure and keep the AudioFile objects in a simple indexed array.  I also want to add category info to the AudioFile object's "category" property.  The error is thrown after I call getDirectoryListing, assign the returned File objects to "content:Array", and then I iterate through "content" assinging each File object to an AudioFile object.  I thought that sense AudioFile is an extension of File that this would not be a problem.  The heart of the issue is how getDirectoryListing returns File objects but I need AudioFile objects.  My next instinct is to override the getDirectoryListing method but I can not find the class declaration for File.
Is there a way to cast the File objects as AudioFile objects?  Should I be using a different strategy for assigning category info to the File objects?  Maybe I should not be extending File class at all.  I am kind of stuck.  Any help would be greatly appreciated.
Here is my code.  Please note that this is my first flex/air/actionscript I ever wrote.  I am using Flash Builder 4.5 and my target is Air Desktop.  The extended class AudioFile is in AudioFile.as.
package
    import flash.filesystem.File;
    public class AudioFile extends File
        public function AudioFile()
        public var category:String;
<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
                        xmlns:s="library://ns.adobe.com/flex/spark"
                           xmlns:mx="library://ns.adobe.com/flex/mx"
                         xmlns:samples="samples.*"
                        applicationComplete="init()" width="386" height="581"
                        initialize="initData()">
    <s:layout>
        <s:VerticalLayout paddingTop="6" paddingLeft="6" paddingRight="6" paddingBottom="6"/>
    </s:layout>
    <fx:Script>
        <![CDATA[
            import AudioFile;
            import flash.events.Event;
            import flash.filesystem.File;
            import mx.collections.ArrayCollection;
            import mx.controls.Alert;
            private var audioObj:AudioFile = new AudioFile();
            protected function init():void
// Center main AIR app window on the screen
                nativeWindow.x = (Capabilities.screenResolutionX - nativeWindow.width) / 2;
                nativeWindow.y = (Capabilities.screenResolutionY - nativeWindow.height) / 2;
                // Get notified when minimize/maximize occurs
                addEventListener(NativeWindowDisplayStateEvent.DISPLAY_STATE_CHANGING, onDisplayStateChange);
// Handles when the app is minimized/maximized
            protected function onDisplayStateChange(e:NativeWindowDisplayStateEvent):void
                trace("Display State Changed from " + e.beforeDisplayState + " to " + e.afterDisplayState);
            private var masterList:ArrayCollection = new ArrayCollection();
            private var dgArray:Array = new Array();
            [Bindable]
            private var initDG:ArrayCollection;
            public function initData():void {
                var initDG:ArrayCollection = new ArrayCollection(dgArray);
            private function analyze():void {
                // ActionScript file
                var sourceDir:AudioFile = getSourceDir();
                var fileList:Array = new Array();
                var dirList:Array = new Array();
                function transverseDirStructure(sourceDir:AudioFile):Array {
                    var flag:Boolean = false;
                    var dirList:Array = new Array();
                    var fileList:Array = new Array();
                    do {
                        var contents:Array = sourceDir.getDirectoryListing();
                        for(var i:int=0;i < contents.length; i++) {
                            // test for isDirectory
                            var file:AudioFile = contents[i];
                            if (file.isDirectory == true) {
                                dirList.push(file);
                            else {
                                fileList.push(file);
                        if (dirList.length == 0)
                            flag = false;
                        else {
                            // recursion
                            fileList = fileList.concat(transverseDirStructure(dirList,fileList));
                    } while (flag == false)
                    return fileList;
                function filterExtensions(fileList:Array):Array {
                    var cleanExtensionsList:Array = new Array();
                    for each (var i:AudioFile in fileList) {
                        if (i.extension == ".wav" || ".aiff") {
                            cleanExtensionsList.push(i);
                    return cleanExtensionsList;
                function filterSize(fileList:Array):Array {
                    var cleanSizeList:Array = new Array();
                    var maxFileSize:int = 350000;
                    for each (var i:AudioFile in fileList) {
                        if (i.size < maxFileSize) {
                            cleanSizeList.push(i);
                    return cleanSizeList;
                function categorizeAudioFiles(fileList:Array):Array {
                    var masterList:Array = new Array();
                    var flag:Boolean = true;
                    var categories:Array = new Array();
                    categories.push("kick","snare","hat","crash","clap");
                    for each (var i:AudioFile in fileList) {
                        for each (var x:String in categories) {
                            if (i.name.search(x) > 0) {
                                // Add name of category to the extended property.
                                i.category = x;
                                masterList.push(i);
                    return masterList;
                fileList = transverseDirStructure(fileList);
                fileList = filterSize(fileList);
                fileList = filterExtensions(fileList);
                fileList = categorizeAudioFiles(fileList);
            private function generateRandom():void {
            private function setDestination():void {
                var file:AudioFile = new AudioFile();
                file.addEventListener(Event.SELECT, dirSelected);
                file.browseForDirectory("Select a directory");
                function dirSelected(e:Event):void {
                    txtDestination.text = file.nativePath;
            private function getDestination():AudioFile {
                var destinationDir:AudioFile = new AudioFile();
                destinationDir.nativePath = txtDestination.text;
                return destinationDir;
            private function getSourceDir():AudioFile {
                var sourceDir:AudioFile = new AudioFile();
                sourceDir.nativePath = txtBrowse1.text;
                return sourceDir;
            private function setSourceDir():void {
                var file:AudioFile = new AudioFile();
                file.addEventListener(Event.SELECT, dirSelected);
                file.browseForDirectory("Select a directory");
                function dirSelected(e:Event):void {
                    txtBrowse1.text = file.nativePath;
            // Control logic
        ]]>
    </fx:Script>
    <mx:Form width="373" height="113" id="formChooseDirectory1">
        <mx:FormHeading label="1. Choose A Source Directory..." width="315" fontSize="13" fontFamily="Verdana" color="#CF71FF"/>
        <s:Button label="Browse..." fontFamily="Verdana" fontSize="13" color="#CF71FF" id="btnBrowse1" enabled="true" click="setSourceDir()"/>
        <s:TextInput width="333" id="txtBrowse1" enabled="false" text="C:\Users\RokaMic\Bangin Beats"/>
    </mx:Form>
    <mx:Form width="373" height="231" id="formAnalyze">
        <mx:FormHeading label="2. Analyze Samples..." fontFamily="Verdana" fontSize="13" color="#00D8FF" width="245"/>
        <s:Button label="Analyze" fontFamily="Verdana" color="#00D8FF" id="btnAnalyze" enabled="true" click="analyze()"/>
        <mx:DataGrid editable="false" enabled="true" fontFamily="Verdana" color="#00D8FF" width="337" dataProvider="{initDG}">
            <mx:columns>
                <mx:DataGridColumn headerText="File name" dataField="filename" color="#00D8FF" fontFamily="Verdana"/>
                <mx:DataGridColumn headerText="Category" dataField="category" color="#00D8FF" fontFamily="Verdana"/>
            </mx:columns>
        </mx:DataGrid>
    </mx:Form>
    <mx:Form width="374" height="173" id="formGenerate">
        <s:Button label="Generate Drum Kits" width="342" height="52" fontSize="18" fontFamily="Verdana" color="#00FF06" id="btnGenerate1" enabled="true" click="generateRandom()"/>
        <mx:FormItem label="How Many?" fontFamily="Verdana" fontSize="13" color="#00FF00" width="340">
            <s:HSlider width="206" stepSize="1" value="1" minimum="1" maximum="25" id="sliderHowMany" liveDragging="true"/>
        </mx:FormItem>
        <s:Button label="Destination..." color="#00FF00" id="btnDestination" enabled="true" click="setDestination()"/>
        <s:TextInput width="332" id="txtDestination" enabled="false"/>
    </mx:Form>
</s:WindowedApplication>

Answer 1

i copied this from your code:
      function categorizeAudioFiles(fileList:Array):Array {
                    var masterList:Array = new Array();
                    var flag:Boolean = true;
                    var categories:Array = new Array();
                    categories.push("kick","snare","hat","crash","clap");
                    for each (var i:AudioFile in fileList) {
                        for each (var x:String in categories) {
                            if (i.name.search(x) > 0) {
                                // Add name of category to the extended property.
                                i.category = x;
                                masterList.push(i);
                    return masterList;
                fileList = transverseDirStructure(fileList);
                fileList = filterSize(fileList);
                fileList = filterExtensions(fileList);
                fileList = categorizeAudioFiles(fileList);
does that contain line 129?  if so, where are those last 5 lines?
they don't appear to be part of the categorizeAudioFiles() function so there should be a compiler error about that last }.  or, you've nested a named function somewhere.