Unloading an swf file and loading another swf file in as3 - actionscript-3

Question

I want to unload a previously loaded swf file(welcome.swf) and load another swf file(topics.swf) when a user clicks a button that is located inside the first loaded swf file(i.e the button, is nested inside the welcome swf file that is to be unloaded).I have tried all manner of codes but none seems to be working and Im at my wits end.Kindly someone assist.Thanks in advance.Below is the code in my main file and the external swf that is to be unloaded.
Main file
var box:Sprite = new Sprite;
box.x = 0;
box.y = 0;
addChild(box);
var loader = new Loader();
var swfURLReq:URLRequest = new URLRequest("welcome.swf");
loader.load(swfURLReq);
box.addChild(loader);
External swf file
var loader = new Loader();`
button_1.addEventListener(MouseEvent.CLICK, button4);
function button4(event:MouseEvent) {
loader.unloadAndStop();
loader=null;
var SWFRequest:URLRequest = new URLRequest("Topics.swf");
loader.load(SWFRequest);
loader.x = 0;
loader.y = 0;
addChild(loader);
}

Answer 1

I think you should load topics.swf at Main Loader.
So you should access Main Loader from welcome.swf.
Doesn't this code work?
External swf file
button_1.addEventListener(MouseEvent.CLICK, button4);
function button4(event:MouseEvent) {
var target: Object = this;
// Search the Main Loader from child swf.
while (target.parent){
target = target.parent;
if (target is Loader){
var loader:Loader = target as Loader;
var SWFRequest:URLRequest = new URLRequest("Topics.swf");
loader.load(SWFRequest);
break;
}
}
}

Answer 2

I would probably move all the loading/unloading responsibility in a main file, with inner swf just letting the main know about some events inside through loaderInfo.sharedEvents just like this:
main file:
var box:Sprite = new Sprite;
box.x = 0;
box.y = 0;
addChild(box);
var loader = new Loader();
var swfURLReq:URLRequest = new URLRequest("welcome.swf");
loader.load(swfURLReq);
function topicsRequestedHandler(event:Event):void {
loader.contentLoaderInfo.sharedEvents.removeEventListener(
"loadTopics", topicsRequestedHandler);
loader.unloadAndStop();
//load "Topics.swf" here
}
loader.contentLoaderInfo.sharedEvents.addEventListener(
"loadTopics", topicsRequestedHandler);
box.addChild(loader);
and in external file:
button_1.addEventListener(MouseEvent.CLICK, button4);
function button4(event:MouseEvent) {
loaderInfo.sharedEvents.dispatchEvent(new Event("loadTopics"));
}
(not tested but should work)
So using this scheme for all the loaded files, you will keep loading/unloading management in one place.