How to spawn objects in array without repeating? - actionscript-3

Question

I have MC's rockThrowers that are added to the stage in 3 different positions. They spawn randomly using a random generator which is working fine. The user clicks a button on the stage and the rockThrowers are added to the stage and pushed in their own array aRockThrowerArray I want to be able to check which of 3 positions they spawned on and not overlap the next rockThrowers that are added to the stage and if so then add a new one to the empty positions. I have tried different strategies mainly booleans and calling them from their own class to my main class but nothing seems to work. Here is my
rockThrowers Class:
private function startPosition():void
{
// y position
this.y = (stage.stageHeight / 2) + 200;
//Start Speed
nSpeed = randomNumber(5, 8);
leftScreenSpawn = randomNumber(1, 3);
//For Left Screen
leftNeg = (stage.stageWidth / 2) - 200;
leftMiddle = (stage.stageWidth / 2) - 150;
leftPos = (stage.stageWidth / 2) - 100;
//Left Screen
if (leftScreenSpawn == 1)
{
this.x = leftNeg;
bLeftNeg = true; // Now if the left Rock thrower is destroyed then turn back to false on main engine class
}else
if (leftScreenSpawn == 2)
{
this.x = leftMiddle;
bLeftMiddle = true;
}else
if (leftScreenSpawn == 3)
{
this.x = leftPos;
bLeftPos = true;
}
//Move
startMoving();
}
Now in my Main Class I have it setup like so for when the user clicks the left screen Btn:
private function rockThrowerSpawn(e:MouseEvent):void
{
//Instantiate screens before hand
rockThrowerSpawnScreen.x = (stage.stageWidth / 2);
rockThrowerSpawnScreen.y = (stage.stageHeight / 2) + 200;
addChild(rockThrowerSpawnScreen);
rockThrowerSpawnScreen.left.addEventListener(MouseEvent.CLICK, chooseSpawnSideRockThrowers);
}
Then the Spawn Function:
private function chooseSpawnSideRockThrowers(e:MouseEvent):void
{
if (e.currentTarget == rockThrowerSpawnScreen.left) // Spawn LEFT
{
//add new rock thrower
rockThrowers = new mcRockThrowers();
//Add object
addChild(rockThrowers);
//Add to Array
aRockThrowerArray.push(rockThrowers);
//trace("LEFT SPAWN");
}
//Subtract resources and update text
nResources -= 10;
updateResourceTextField();
//Remove Listeners
rockThrowerSpawnScreen.left.removeEventListener(MouseEvent.CLICK, chooseSpawnSideRockThrowers);
rockThrowerSpawnScreen.destroy();
}
I understand that this alone will always spawn random positions I deleted everything that wasn't working now I'm back to this square one. Any ideas on how I can accomplish this? All support is appreciate.

Answer 1

Easy. You need a finite Array that produces 3 values in a random order.
var L:Array =
[
(stage.stageWidth / 2) - 200,
(stage.stageWidth / 2) - 150,
(stage.stageWidth / 2) - 100,
];
function fetchPosition():Number
{
// Get a random index based on the current length of L.
var anIndex:int = Math.random() * L.length;
// Record the result.
var result:Number = L[anIndex];
// Remove the result from the list.
L.splice(anIndex, 1);
return result;
}
So, you can validly call fetchPosition() three times per application run, and each run the contents of L will be fetched in random order and, more importantly, you won't get the same value twice, because the fetched value is removed from the data set.