Haxe: Calling a function from and outside Class within Main Class - game-engine

Question

I would like to call a function that is located outside the Main class of my Haxe game.
I am able to add bubbles to the game using: addChild(new Bubble(player.x, player.y));
I would like to update the game without using an EventListener in each added object.
The follow code: Bubble.tick();
Yields this error when run from main:
Bubble has no field tick
Bubble Class:
package;
import flash.Lib;
import flash.display.Bitmap;
import flash.display.BitmapData;
import flash.display.Sprite;
import flash.display.MovieClip;
import openfl.Assets;
import flash.events.Event;
class Bubble extends Sprite
{
private var newBubble:Bitmap;
private static var gameBubble:Array<Sprite> = new Array<Sprite>();
public function new (xpos:Float,ypos:Float) {
super ();
this.x = xpos;
this.y = ypos;
newBubble = new Bitmap (Assets.getBitmapData ("img/sprite_bubble_16x16.png"));
newBubble.x = -12.5;
newBubble.y = -12.5;
addChild(newBubble);
gameBubble.push(this);
trace("Bubble");
}
private function tick2(e:Event) {
this.y -= 5;
checkPop();
}
public function tick() {
this.y -= 5;
checkPop();
}
private function checkPop() {
if(this.y < 0) {
this.parent.removeChild(this);
}
}
}

Answer 1

tick is a member method, not a static method.
Bubble.tick()
will look for static public function tick(), while
var b = new Bubble();
b.tick();
will look for public function tick().
Static functions are tied to the class, not a specific instance of the object. Member functions are tied to a specific instance of an object, and can use this to access that instance.
Hope that helps
EDIT (in response to your comment):
It's hard to tell exactly what you are trying to do, but it looks like you want each "Bubble" to slowly move towards the bottom of the screen, and to be removed when it does.
You have 2 options:
1) Every bubble instance creates it's own timer, and tick is a member function (public function tick) which does this.y -= 5 etc.
2) tick is a static function (static public function tick) which does a loop over every bubble (for (bubble in gameBubble) { bubble.y-=5; ...etc... })
The basic rule: anything static can't access this, because it doesn't know which bubble you are talking about, so you'll have to use your static array to go through each of them.