How to add new increase the pool rather then trowing a error.

Question

Im trying to build a game and after many attempts and hours of thinking i did manage to create something that looks like a game.The problem now is that there are so many objects that are constantly creating and removing from the stage. that the game is starting to slow down(it is laggy.).So i have searched the net and understood that i will have to use a "Object pooling Method" rather than creating and removing the objects after i dont have any use of them any more, if i want to make the game more memory friendly.
At first i didnt want to use this method (object pooling) ,but after a while i understood that i dont have a lot of options.So i started to search how and why and how.
Yet in this example im just trying this for the bullets (for now) cause if i can do it for them, i can manage to do it for other objects and projects (it will be simple for me to understand what is happening ., what am i doing , when do i add an existing object from the pool and when im creating a new one(when there are non left, things like this)
i did copy some part of this code from a tutorial that i found in the net but , from then i dont know how to increase the pool rather than throwing this error. I did try to create a new object or to increase the pool length but .... it is not working so im sure that im not doing something the way it must be done.
so i have this so far :
its a "simple" pool that calls a simple shape class (circle dot) and gives that to the main stage when the "SPACE" button is pressed
package
          import flash.display.Sprite;
          import flash.events.Event;
          import flash.display.Bitmap;
          import flash.display.BitmapData;
          import flash.display.Shape;
          public class Bullet extends Sprite{
                    public var  rectangle:Shape = new Shape();
                    public function Bullet(){
                              super();
                              addEventListener(Event.ADDED_TO_STAGE, init);
                              graphics.beginFill(0xFF0000);
                              graphics.drawRect(-5, -5, 10,10);
                              graphics.endFill();
                    private function init(event:Event):void{
the SpritePool where i cant figure out how to replace the throw new error with some new code that will increase the pool
package {
          import flash.display.DisplayObject;
          public class SpritePool {
                    private var pool:Array;
                    private var counter:int;
                    public function SpritePool(type:Class, len:int) {
                              pool = new Array();
                              counter = len;
                              var i:int = len;
                              while (--i > -1) {
                                        pool[i] = new type();
                    public function getSprite():DisplayObject {
                              if (counter > 0) {
                                        return pool[--counter];
                              } else {
                                        throw new Error("You exhausted the pool!");
                    public function returnSprite(s:DisplayObject):void {
                              pool[counter++] = s;
and the Game class (the documents class)
package {
          import flash.ui.Keyboard;
          import flash.display.Sprite;
          import flash.events.Event;
          import flash.events.KeyboardEvent;
          import flash.display.Bitmap;
          import flash.display.BitmapData;
          import flash.display.Shape;
          public class Game extends Sprite {
                    private var ship:Shape;
                    private var bullets:Array;
                    private var pool:SpritePool;
                    public function Game() {
                              Assets.init();
                              addEventListener(Event.ADDED_TO_STAGE, init);
                    private function init(event:Event):void {
                              pool = new SpritePool(Bullet,10);
                              bullets = new Array();
                              ship = new Shape();
                              ship.graphics.beginFill(0xFF00FF);
                              ship.graphics.drawRect(0,0, 60, 60);
                              ship.graphics.endFill();
                              ship.x = stage.stageWidth / 2 - ship.width / 2;
                              ship.y = stage.stageHeight - ship.height;
                              addChild(ship);
                              stage.addEventListener(KeyboardEvent.KEY_DOWN, onDown);
                              addEventListener(Event.ENTER_FRAME, loop);
                    private function onDown(event:KeyboardEvent):void {
                              if (event.keyCode == Keyboard.SPACE) {
                                        var b:Bullet = pool.getSprite() as Bullet;
                                        b.x = ship.x + ship.width / 2;
                                        b.y = ship.y;
                                        addChild(b);
                                        bullets.push(b);
                                        trace("Bullet fired");
                    private function loop(event:Event):void {
                              for (var i:int=bullets.length-1; i>=0; i--) {
                                        var b:Bullet = bullets[i];
                                        b.y -=  10;
                                        if (b.y < 0) {
                                                  bullets.splice(i, 1);
                                                  removeChild(b);
                                                  pool.returnSprite(b);
                                                  trace("Bullet disposed");
any suggestions/help how to do it

Answer 1

To put you on the path (the errors/events needs formalization), here would be a quick example. Your pool class:
package
          import flash.display.DisplayObject;
          public class SpritePool
                    private var pool:Array;
                    private var counter:int;
                    private var classRef:Class;
                    // public get to know what's left in the pool
                    public function get availableObjects():int
                              return counter;
                    public function SpritePool(type:Class, len:int)
                              classRef = type;
                              pool = new Array();
                              counter = len;
                              var i:int = len;
                              while (--i > -1)
                                        pool[i] = new classRef();
                    public function getSprite():DisplayObject
                              if (counter > 0)
                                        return pool[--counter];
                              else
                                        throw new Error("PoolExhausted");
                    public function returnSprite(s:DisplayObject):void
                              pool[counter++] = s;
                    public function increasePool(amount:int):void
                              counter += amount;
                              while (--amount > -1)
                                        pool.push(new classRef());
                    public function decreasePool(amount:int):void
                              if (counter >= amount)
                                        counter -= amount;
                                        pool.splice(counter - amount,amount);
                              else
                                        throw new Error("PoolDecreaseFail");
Now you'd need to be catching those errors. Again, the errors should be formalized or you could use events by extending IEventDispatcher. I kept it simple.
Here would be the simple Bullet class I'm using:
package
          import flash.display.Sprite;
          public class Bullet extends Sprite
                    private var bullet:Sprite;
                    public function Bullet():void
                              var bullet:Sprite = new Sprite();
                              bullet.graphics.beginFill(0xFF0000,1);
                              bullet.graphics.drawCircle(-5,-5,10);
                              bullet.graphics.endFill();
                              addChild(bullet);
Just draws a red circle just to visualize it..
Here would be a full example of using it. It will import both of these classes (saved as SpritePool.as and Bullet.as in the same folder). Paste this in the actions panel on frame 1:
import SpritePool;
import Bullet; // a simple red 10px circle
import flash.display.Sprite;
import flash.utils.setTimeout;
// fill the pool, swim trunks optional
var pool:SpritePool = new SpritePool(Bullet, 10);
// grab some objects from the pool
// array of currently held objects
var myBullets:Array = new Array();
while (pool.availableObjects > 0)
          myBullets.push(pool.getSprite());
// display in random positions
for (var i:int = 0; i < myBullets.length; i++)
          addChild(myBullets[i]);
          // position
          myBullets[i].x = int(Math.random()*stage.stageWidth);
          myBullets[i].y = int(Math.random()*stage.stageHeight);
trace("myBullets has " + myBullets.length + " bullets! pool has " + pool.availableObjects + " left.");
// now I want one more, but I should check for errors
try
          // fail, none left!
          myBullets.push(pool.getSprite());
catch (e:*)
          // this should be a custom event, but for speed, quick and dirty
          if (e == 'Error: PoolExhausted')
                    trace("D'oh no more bullets! I need more!");
                    pool.increasePool(10);
                    trace("Added 10 more, now available in pool " + pool.availableObjects);
// try to reduce the pool by 15, which should error
try
          pool.decreasePool(15);
catch (e:*)
          // again should be a formal error
          if (e == 'Error: PoolDecreaseFail')
                    trace("Oops, can't reduce pool by 15! Let's trim all extras, available is " + pool.availableObjects);
                    // we know it'll work, no error checking
                    pool.decreasePool(pool.availableObjects);
                    trace("Left in pool: " + pool.availableObjects);
// now lets wait 5 seconds and remove it all back to the pool
setTimeout(ReturnToPool,5000);
function ReturnToPool():void
          // now let's just return all the objects to the pool
          while (myBullets.length > 0)
                    removeChild(myBullets[myBullets.length - 1]);
                    pool.returnSprite(myBullets.pop());
          // now check the pool, should have 10
          trace("Amount of bullets in use " + myBullets.length + ", in pool " + pool.availableObjects);
For ease you can just download my example source (saved down to CS5).
Anything from here is just symantics. For example instead of throwing an error because the pool is too small you could simply increase the pool by a fixed amount yourself and return the objects requested.
To keep objects as low as possible you could use a timer to measure the amount of objects in use over a duration and reduce the pool appropriately, knowing the pool will grow as it needs.
All of this is just to avoid unnecessary object creation.
BTW here's my trace which should match yours:
myBullets has 10 bullets! pool has 0 left.
D'oh no more bullets! I need more!
Added 10 more, now available in pool 10
Oops, can't reduce pool by 15! Let's trim all extras, available is 10
Left in pool: 0
(after 5 seconds)
Amount of bullets in use 0, in pool 10