CODEWITHSUNDEEP
ooptypescript
Nigh7Sh4de
Nigh7Sh4de

Reputation: 455

TypeScript Access Static Variables Using Instances

So in most OOP languages static variables can also be called class variables, ie their value is shared among all instances of this class. For example, in my game I have a class Bullet which is extended by GreenBullet and PinkBullet. I want these subclasses to have a "class" or "static" variable called ammo so that I can keep track of the ammo count for that specific ammo type. But here is the catch: I want to be able to access this property through an instance of the subclass.

Example:

var bullet: GreenBullet = new GreenBullet()
if (bullet.ammo <= 0)
    return;
bullet.shoot();
bullet.ammo --;

I want ALL instances of GreenBullet to be aware of this change to their ammo count.

Upvotes: 9

Views: 28882

Answers (1)

zlumer
zlumer

Reputation: 7004

First option is to create instance accessors to static variable:

class GreenBullet
{
   static ammo: number = 0;
   get ammo(): number { return GreenBullet.ammo; }
   set ammo(val: number) { GreenBullet.ammo = val; }
}
var b1 = new GreenBullet();
b1.ammo = 50;
var b2 = new GreenBullet();
console.log(b2.ammo); // 50

If you want all subclasses of Bullet (including itself) to have separate ammo count, you can make it that way:

class Bullet
{
   static ammo: number = 0;
   get ammo(): number { return this.constructor["ammo"]; }
   set ammo(val: number) { this.constructor["ammo"] = val; }
}
class GreenBullet extends Bullet { }
class PinkBullet extends Bullet { }

var b1 = new GreenBullet();
b1.ammo = 50;
var b2 = new GreenBullet();
console.log(b2.ammo); // 50
var b3 = new PinkBullet();
console.log(b3.ammo); // 0

On a side note, I'm fairly sure you should not store bullet count in a static variable.

Upvotes: 18

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