AS3 Error 1009 - Where am i going wrong? - actionscript-3

Question

This is the error I'm getting:
TypeError: Error #1009: Cannot access a property or method of a null object reference. at ICA_v7_fla::MainTimeline/addEgg()
at Function/http://adobe.com/AS3/2006/builtin::apply()
at SetIntervalTimer/onTimer()
at flash.utils::Timer/_timerDispatch()
at flash.utils::Timer/tick()
Cannot see where I am going wrong - could someone point out where I'm trying to refer to a null object reference please :)
The rest of my AS reads:
import flash.events.Event;
import flash.utils.Timer;
import flash.events.TimerEvent;
//Set as a variable so that it can be changed at a later
//date so that the user level can change (if necessary).
var eggMoveSpeed=6;
var Score=0;
var ScoreValue=10;
var Level=1;
var NextLevel=100;
var EggCount=0;
var EggMax=15;
btn.addEventListener(MouseEvent.CLICK, scorer);
function scorer(e:Event):void{
//Add to the score.
Score=Score+10;
//Display score in text box.
scoreText.text=Score;
}
var eggAdd = setInterval(addEgg,2000);
function addEgg(){
//Add to the egg count (to ensure maximum is not exceeded).
EggCount=EggCount+1;
if (EggCount<=EggMax){
//Create an object of the egg_mc from the egg class.
var egg:egg_mc = new egg_mc();
//Set the Max and Min WIDTH positions.
var maxWidth = 452;
var minWidth = 98;
//Randomize the position of the egg on the screen - with thanks to http://www.kirupa.com/developer/actionscript/tricks/random.htm
var positionX = Math.floor(Math.random()*(1+maxWidth-minWidth))+minWidth;
//Position the egg on the stage, and add it to the screen
egg.y=400;
egg.x=positionX;
//Add the egg to the stage.
stage.addChild(egg);
//Add a moving loop to the egg.
egg.addEventListener(Event.ENTER_FRAME, loop);
}else{
clearInterval(eggAdd);
}
function loop(e:Event):void{
//Move the egg up the screen.
egg.y-=eggMoveSpeed;
//Check to see if egg has got to the top of the screen - if so, then move the object to the bottom.
if (egg.y<-100){
egg.y=400;
}
}
//Add an event listener to the egg, to see if it has been clicked.
egg.addEventListener(MouseEvent.CLICK, clickedEgg);
function clickedEgg(e:Event):void{
//http://asgamer.com/2009/flash-game-design-basics-adding-library-objects-to-stage-with-as3
//Create an object of the brokenEgg_mc from the broken egg class.
var brokenEgg:brokenEgg_mc = new brokenEgg_mc();
//Position the brokenEgg image wherever the egg Image was.
brokenEgg.y=egg.y;
brokenEgg.x=egg.x;
//Add brokenEgg to stage, and remove the egg image.
stage.addChild(brokenEgg);
stage.removeChild(egg);
//Add to the score.
Score=Score+ScoreValue;
//Display score in text box.
scoreText.text=Score;
//Set LevelCheck Variable to 0 - to recalculate correctly.
var LevelCheck = 0;
//Check the level that the user is currently on by dividing the score by the next level required score.
LevelCheck=Score/NextLevel;
//Setup a variable to use for the actual level to display.
var ActualLevel=0;
//Check to see if the LevelCheck variable has come back less than 1 (i.e. 0.1 or a score of 10).
if (LevelCheck < 1){
//If yes, then set the level to 1, as user is still on level 1.
ActualLevel=0;
} else {
//If not, then round down to the lowest level (1.9 is still level 1!).
ActualLevel=Math.floor(LevelCheck);
}
//Display the Lowest Level to the user.
levelText.text=ActualLevel;
}}
Obviously, the timer event loops until there are 15 eggs on the stage, where the interval should then stop running - but this produces the error.

Answer 1

Your egg variable is function-wide, namely it's defined in addEgg() function, but you refer to egg inside clickedEgg and loop, which don't have actual access to egg's value. Also, if there is more than a single egg, how do you plan on tracking which egg was clicked, etc? At the very least, use e.target in clickedEgg function to find out what egg was clicked, and don't forget clearing the event listener.
function addEgg():void {
if (EggCounter>=EggMax) return; // why adding eggs if there are too many?
var egg:egg_mc=new egg_mc();
// rest of code intact
}
function loop(e:Event):void {
var egg:egg_mc=(e.target as egg_mc);
if (!egg) return; // loop is for eggs only
// rest of function intact
}
function clickedEgg(e:MouseEvent):void {
var egg:egg_mc=(e.target as egg_mc);
if (!egg) return;
// rest of function intact, as we now have a valid egg link
egg.removeEventListener(Event.ENTER_FRAME,loop);
egg.removeEventListener(MouseEvent.CLICK,clickedEgg);
// clear listeners. These are persistent until removed manually!
}