Multiple URLs, Error #1109

Question

Hello,
I am new to Flash and AS3 so please bear with me
I'm trying to complete an ad project that will go on my institution's website. There are five ads (movie clips) that will cycle through once before stopping. From there, the user can hit a nav button (four movie clips) to view a particular ad and click on it, taking them to an outside website or a page on our own site. However, I've hit a snag involving Error #1109.
Here's the actionscript I'm using for the first ad (which works fine):
var url1:URLRequest = new URLRequest ("http://www.google.com");
function onClick1(event:MouseEvent):void
        navigateToURL(url1);
advert1.addEventListener(MouseEvent.CLICK, onClick1);
advert1.buttonMode = true;
When I copy, paste and make changes for the second link, like this:
var url2:URLRequest = new URLRequest ("http://www.cnn.com");
function onClick2(event:MouseEvent):void
        navigateToURL(url2);
advert2.addEventListener(MouseEvent.CLICK, onClick2);
advert2.buttonMode = true;
I get the 1109 error:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at NBPL_ad_fla::MainTimeline/frame1()
What does this mean, exactly?
I've been scouring the web for solutions and those that I manage to locate either a) don't work or b) involve ActionScript techniques I'm not familiar with.
Any help offered would be greatly, greatly appreciated.

Answer 1

First thing - the error.
Double and triple check that you have a symbol on the stage with the instance name "advert2"  That is the likely culprit here.
Now then, for a quick method to consolidate that code into 1 click handler.  This type of thing can come in handy later, especially if you keep adding more ads to the project.  This will help keep your variables in check.
var url1:URLRequest = new URLRequest("http://www.google.com");
var url2:URLRequest = new URLRequest("http://www.cnn.com");
function onClick(event:MouseEvent):void {
     var nam:String = event.currentTarget.name.split("advert")[1];
     var urlS:String = "url"+nam;
     navigateToURL(this[urlS]);
advert1.buttonMode = true;
advert2.buttonMode = true;
advert1.addEventListener(MouseEvent.CLICK,onClick);
advert2.addEventListener(MouseEvent.CLICK,onClick);
A slightly better method would involve an array:
var urlArray:Array = new Array();
urlArray.push("");
urlArray.push("http://www.google.com");
urlArray.push("http://www.cnn.com");
function onClick(event:MouseEvent):void {
     var nam:Number = Number(event.currentTarget.name.split("_")[1]);
     navigateToURL(new URLRequest(urlArray[nam]));
advert_1.buttonMode = true;
advert_2.buttonMode = true;
advert_1.addEventListener(MouseEvent.CLICK,onClick);
advert_2.addEventListener(MouseEvent.CLICK,onClick);