Question

I have a basic space shooter game made in AS3.

The game currently consists out of one enemy and the player – a movable turret.

The premise of the game is, when the enemy is shot, it respawns, and the player score goes up with one point.

Now I want to extend the game by having more than one enemy on the playing field. The amount of enemies can differ for each wave, so I do not really want to keep track of them individually.

When I want to create an enemy, I call (from within my main class)

this.addChild(createNewEnemy());

with the createNewEnemy() function creating, and returning an anonymous Enemy object.

My question is, how do I perform hit tests on these anonymous Enemies with the bullet being fired by the player? When an enemy collides with a bullet, it should be removed and the score should be incremented.

Answer 1

I’m not quite sure what you mean by “anonymous object.” You really ought to be creating these things in such a way that can track them. One way would be perhaps override your addChild method for the container sprite and push new enemies to a vector. Example:

var enemies:Vector.<Enemy> = new Vector.<Enemy>();

override public function addChild(child:DisplayObject):DisplayObject
{
    if(child is Enemy) {
       enemies.push(child);
    }
    super.addChild(child);
}

Now you can simply test against the enemies vector, or use the same “is” keyword in your bullet collision to check and see if the colliding display object is of based type Enemy.

As far as the actual code to do the collision detection, see the following answer: https://stackoverflow.com/a/7083965/562566