AS3: 1180 Call to a possibly undefined property: Add Child - actionscript-3

Question

Pretty big noob at AS3. I'm trying to Load a SWF into another file. (Main .fla loading external SWFS on mouse click)
I keep getting the error: 1180 Call to a possibly undefined property: Add Child, however.
My LoadSWF code is:
package {
import flash.display.*;
import flash.events.*;
import flash.net.*;
public class LoadSWF {
private var loaderFile: Loader;
private var swfFile: Object;
private var sourceFile: String;
private var fileLabel: String;
private var canDrag: Boolean;
private var popX: int;
private var popY: int;
public function LoadSWF(myFile: String, myLabel: String, myX: int = 0, myY: int = 0, myDrag: Boolean = false) {
// constructor code
trace("Loading SWF file:", myFile);
sourceFile = myFile;
fileLabel = myLabel;
canDrag = myDrag;
popX = myX;
popY = myY;
openSWF();
}
private function openSWF(): void {
// initialise variables
loaderFile = new Loader();
swfFile = addChild(loaderFile);
// set initial position of the SWF popup
loaderFile.x = popX;
loaderFile.y = popY;
try {
loaderFile.load(new URLRequest(sourceFile));
// runs after the SWF popup has finished loading
loaderFile.contentLoaderInfo.addEventListener(Event.COMPLETE, SWFloaded);
} catch (err: Error) {
// provide some error messages to help with debugging
trace("Error loading requested document:", sourceFile);
trace("Error:", err);
sourceFile = null;
}
} //end openSWF
private function SWFloaded(evt: Event): void {
// and add the required event listeners
loaderFile.addEventListener(MouseEvent.MOUSE_DOWN, dragSWF);
loaderFile.addEventListener(MouseEvent.MOUSE_UP, dropSWF);
// use the POPUP reference to access MovieClip content
swfFile.content.gotoAndStop(fileLabel);
// assigns a close function to the button inside the popup
swfFile.content.closeBtn.addEventListener(MouseEvent.CLICK, closeSWF);
// remove the COMPLETE event listener as it’s no longer needed
loaderFile.contentLoaderInfo.removeEventListener(Event.COMPLETE, SWFloaded);
} //end SWFLOaded
private function dragSWF(evt: MouseEvent): void {
swfFile.content.startDrag();
}
private function dropSWF(evt: MouseEvent): void {
swfFile.content.stopDrag();
}
private function closeSWF(evt: MouseEvent): void {
// remove the required event listeners first
loaderFile.removeEventListener(MouseEvent.MOUSE_DOWN, dragSWF);
loaderFile.removeEventListener(MouseEvent.MOUSE_UP, dropSWF);
swfFile.content.closeBtn.removeEventListener(MouseEvent.CLICK, closeSWF);
// remove the pop-up
loaderFile.unloadAndStop();
}
} //end class
} //end package
I'm calling it into my main class file, which code is (I left out the rest, guessing its unnecessary):
package {
import flash.display.MovieClip;
import flash.text.TextField;
import flash.display.SimpleButton;
import flash.utils.Dictionary;
import flash.text.TextFormat;
import flash.net.*;
import flash.events.*;
import fl.controls.*;
import flash.media.*;
import fl.events.ComponentEvent;
import fl.managers.StyleManager;
import fl.data.DataProvider;
import fl.data.SimpleCollectionItem;
import fl.managers.StyleManager;
import fl.events.ComponentEvent;
import flash.events.Event;
import flash.net.SharedObject;
import LoadSWF;
public class Main extends MovieClip {
//Declare variables
private var componentFmt: TextFormat;
private var radioBtnFmt: TextFormat;
private var playerData: Object;
private var savedGameData: SharedObject;
// Pop-up Variables
private var popupFile: LoadSWF;
private var swfPath: String;
public function Main() {
// constructor code
this.savedGameData = SharedObject.getLocal("savedPlayerData");
this.setComponents();
this.setPlayerData();
//this.swfPath = "";
//this.isHelpOpen = false;
//this.sndPath = "musicSFX/music2.mp3";
//this.isMuted = false;
//this.sndTrack = new LoadSND(this.sndPath, this.canRepeat);;
//this.muteBtn.addEventListener(MouseEvent.CLICK, this.setMute);
swfPath = "";
helpBtn.addEventListener(MouseEvent.CLICK, openSWF);
//hauntedForestBtn.addEventListener(MouseEvent.CLICK, openSWF);
}
public function openSWF(evt: MouseEvent): void {
// determine which button was pressed
var myFile: String = evt.currentTarget.name.replace("Btn", ".swf");
myFile = (swfPath == "") ? myFile : swfPath + myFile;
if (myFile == "help.swf") {
// load the help SWF file - is draggable
swfFile = new LoadSWF(myFile, currentFrameLabel, 80, 60, true);
} else {
// load the selected SWF file - is not draggable
swfFile = new LoadSWF(myFile, currentFrameLabel);
}
addChild(swfFile);
}
If anyone could help me find a solution, i'd greatly appreciate it.
Thanks :)

Answer 1

addChild is defined by DisplayObjectContainer.
So to access this function, you'll have to alter LoadSWF so that it extends DisplayObjectContainer.