NullReferenceException

Unity Engine
1

hello i am reading the unity 3x game development i am following Prototyping and Scripting Basics bit of the the book.i made the game were u shoot by left clicking at the brick wall the game run but as soon as it does.I get a NullReferenceException: Object reference not set to an instance of an object Shooter.Update () (at Assets/Prefabs/Shooter.js:12) error here is my script

var bullet : Rigidbody;
var power : float = 1500;
var moveSpeed : float = 5;

function Update () {
var h : float = Input.GetAxis("Horizontal") * Time.deltaTime * moveSpeed;
var v : float = Input.GetAxis("Vertical") * Time.deltaTime * moveSpeed;
transform.Translate(h, v, 0);
if(Input.GetButtonUp("Fire1"))
var instance: Rigidbody = Instantiate(bullet, transform.position,transform.rotation);
var fwd: Vector3 = transform.TransformDirection(Vector3.forward);
instance.AddForce(fwd * power);  
}
2

Did you associate the bullet variable with something in the inspector?

3

yes i did it still comes up with the error.

4

The script seems fine. If you dragged your bullet rigidbody from the hierarchy, that could be your problem (might get destroyed or something before the script gets the reference).

Also, code tags are a very good thing :).

5

how alse can i associate the bullet variable then.

6

Make it a prefab.

7

still dose not work.

8

Alright, checked your script again,. There are no curly brackets for your if statement, so only the next statement is conditional. If the bullet isn’t instantiated there won’t be an instance variable, but the script tries to access one regardless.

var bullet : Rigidbody;

var power : float = 1500;

var moveSpeed : float = 5;

 

function Update () {

var h : float = Input.GetAxis("Horizontal") * Time.deltaTime * moveSpeed;

var v : float = Input.GetAxis("Vertical") * Time.deltaTime * moveSpeed;

transform.Translate(h, v, 0);

if(Input.GetButtonUp("Fire1"))
{
var instance: Rigidbody = Instantiate(bullet, transform.position,transform.rotation);

var fwd: Vector3 = transform.TransformDirection(Vector3.forward);

instance.AddForce(fwd * power);  
}
}
9

thank you so much tanel it works.