how to match as3 function type declaration with differing calls?

private function playSound():void 
{ 
_soundChannel = _soundObj.play(); 
_soundChannel.addEventListener(Event.SOUND_COMPLETE, nextTrack);
} 
<s:Button width="35" label=">>" click="nextTrack();"/> 

Assuming the nextSound() function looks the same as playSound, typewise... The button click works fine, but the event listener won't call the function because its sending an argument the functi开发者_开发问答on isn't expecting. I can change the nextTrack function to be evt:Event, but then the button is sending not enough arguments, and I can't find anything to type it to that will work. I can make a typed function to call the un-typed nextTrack function from the event listener

public function callnextsong(evt:Event):void{
                nextTrack();
            }

But i feel like there's probably a less circuitous way of accomplishing it!

Use a default parameter:

public function nextTrack(evt:Event = null):void {

It can then be called with or without the caller supplying a parameter.