NullReferenceException

Unity Engine
1

Everything in my script works fine, however I keep getting this error:

NullReferenceException: Object reference not set to an instance of an object
LaserFire.Update () (at Assets/Scripts/LaserFire.js:40)

the line of code is:

laserBeam.rigidbody.AddForce(transform.forward * 200);

I broke string apart to help narrow where the problem is. So the only part that is on line 40 is:

(transform.forward * 200);

I don’t see where the issue is with that? can anybody help?

2

Other causes could be that you didnt assing anything to ‘laserBeam’ or that you didnt apply a rigidbody to the laserBeam object.

3

"laserBeam refers to a prefab, and Yes, it does have a rigidbody on it :frowning:

4

It is rather strange that you are trying to add force to a prefab. Could be that it doesn’t have rigidbody on it because it’s not instantiated.

You can narrow the problem more by putting null checks or by splitting the expression into several parts (not just putting some whitespace as debugger will just ignore them)

5

The prefab “laserBeam,” is set up as a projectile that originates from a spawn point. I got the script from the following tutorial:

could you elaborate more on your solution for the null checks or splitting the expression into several parts? (I’m very new to scripting)

6

If your variable laserBeam is your prefab, then that would explain why this isn’t working. You need to add force to an instance of the prefab, not the prefab itself.

Looking at that tutorial, the closest thing I can spot to your code is a case of instantiating a “Bullit”, where he has a variable called BullitPrefab, then uses Instantiate and assigns the result to a variable called Bullit, then adds force to the rigid body of the newly created instance.

Are you doing the same thing? Also, in future, it’ll be helpful if you post more of your code, it’s difficult to tell where you’ve gone wrong from a single line.

7

That helps shine some light on this for me. So, I have my script attached to my gameObject “Gun01,” and my “laserBeam” prefab instance has a Rigidbody attached to it. But now insteand of shooting forward, the shot goes straight down the -Y axis (gravity is off). I’m still getting the same error. Here is the entire script that I’m using. The script is suppose to me a component of the “Gun01” right?

1221546–50487–$LaserFire.js (699 Bytes)

8

The best way to post code is to wrap it in code tags, like this : [CODE]code goes here[/CODE]

So other people can follow along, here is your code :

var laserBeamPrefab : Transform;

function Update ()

{

	if(Input.GetButtonDown("Jump"))
	

	var laserBeam = Instantiate(laserBeamPrefab, GameObject.Find("spawnPoint").transform.position,Quaternion.identity);
    
    laserBeam.rigidbody.AddForce(transform.forward * 200);
    
   
}

Your null reference is being caused by your if statement. When you don’t include { }'s, the if statement evaluates the next line when the condition is true. So whenever the jump button is pushed, it is instantiating a laserbeam. However, the line after that, where you add force, is run every frame regardless of if the button was pushed (it’s outside the if statement). Since you’re adding force to an object that was never created, it’s a null reference.

You’ll want to define a block of code using { }, like this

if(Input.GetButtonDown("Jump")) {
   var laserBeam = Instantiate(laserBeamPrefab, GameObject.Find("spawnPoint").transform.position,Quaternion.identity);
   laserBeam.rigidbody.AddForce(transform.forward * 200);
}