increasing a var in one script from another

Unity Engine
1

I want to increase my ammo count when my missles are destoryed
ammoCount is on the launcher script and destory is on the missle script - so I want to increase ammoCount from my missle script

I have got a bit lost but I was trying

Missle.js

var addAmmo:Launcher;

function OnCollisionEnter(collision : Collision) {
..../etc
Destroy (gameObject);
addAmmo.ammoCount + 1;

but it complains about NullReferenceException

Launcher.js

public var ammoCount = 4;

function Update () { 
if (...etc..

    instantiatedProjectile.velocity = transform.forward * speed; 
    ammoCount --;
2

A couple things that might be happening:

The reference to instantiatedProjectile in your Launcher script might point to null if the instantiatedProjectile has already been destroyed. I can’t tell for sure if this would ever happen, though.

Also, I notice that you’re calling Destroy in your Missile script before you add to your ammo count. This means that the ammoCount line won’t ever get called.

3

The problem is probably that the missile var addAmmo:Launcher; is set to be something in a scene and then the missile is assigned to a prefab and instantiated. This will break that link. In your missile instantiator you need missile.addAmmo = this;

No. Destroy does not take effect until the next frame.

4

Change the line in Launcher.js that says

public var ammoCount = 4;

to this:

static var ammoCount = 4;

And rename Missle.js to Missile.js ;), and change it to this:

function OnCollisionEnter(collision : Collision) {
..../etc
Destroy (gameObject);
Launcher.ammoCount ++;

(Get rid of the “var” line and change the “addAmmo.ammoCount + 1;” line.)

–Eric

5

Sorry for leading you astray, Adam. :sweat_smile:

6

worked like a dream

7

Although I forgot to say that static variables have the feature of retaining their value from one run to the next. So you probably want to assign the value of ammoCount in a Start function…just declaring it at the top of the script isn’t enough.

–Eric

8

works even more like a dream :smile: