Checking shot collisions and removing shot and target in AS3 - arrays

Question

Last year was my first successful year in teaching my students to create catch and avoid games in Flash with AS3. This year is getting better. Each year I come here for help at least once.
I'm trying to add shooting into the possibilities for their second game project. I can make the shot happen from the ship, gun, whatever, and make it move, and get rid of it when it is off screen, but have not figured out a clean way to have both the shot and the target go away (removeChild and array.splice) upon collision.
The code I have sort of works, but I keep getting the error,
TypeError: Error #1010: A term is undefined and has no properties. at
DropShootV02_fla::MainTimeline/checkShots()
.
Normally I know that this is because of a mismatch between objects and index numbers, but this is related to the call to a second array in removing boxes and bullets.
For simplicity I'll just include the shooting code. Similar organization creates and drops the boxes.
Any help is appreciated. BTW we are not using external script in an AS file.
var shotSpeed = 18;
var shots:Array = new Array();
import flash.events.MouseEvent;
import flash.events.Event;
stage.addEventListener(MouseEvent.CLICK, fireLaser);
function fireLaser(e:MouseEvent):void
{
if (gameOn==true)
{
var shot:Shot=new Shot();
addChild(shot);
shots.push(shot);
shot.gotoAndStop(1);
shot.x = user.x;
shot.y = user.y;
trace(shots.length);
}
}
addEventListener(Event.ENTER_FRAME, moveShot);
function moveShot(e:Event):void
{
for (var i:int=shots.length-1; i>=0; i--)
{
shots[i].y -= shotSpeed;
if (shots[i].y < -25)
{
removeChild(shots[i]);
shots.splice(i,1);
}
}
}
addEventListener(Event.ENTER_FRAME, checkShots);
function checkShots(e:Event):void
{
for (var i:int=shots.length-1; i>=0; i--)
{
for (var k:int=boxes.length-1; k>=0; k--)
{
if (shots[i].hitTestObject(boxes[k]))
{
if (boxes[i].type == "good")
{
score--;
scoreDisplay.text = "Score:" + score;
}
if (boxes[i].type == "bad")
{
score++;
}
removeChild(boxes[k]);
boxes.splice(k,1);
//if I leave this part out I get no errors,
//but but the bullet goes on to strike again
removeChild(shots[i]);
shots.splice(i,1);
}
}
}
}
Thanks kaarto:
I had tried that previously and kept getting the same error. I used that elsewhere in this game code. Turns out I needed to moderate how often the player was shooting. I changed from shooting with the mouse to using space instead and now the problem is gone. Break is definitely a good one here.

Answer 1

Merge move shot and checkShots in one ENTER_FRAME handler.