Prefab and bullet not instantiating on a weapon

Unity Engine
,
1

Hey,

So I’m trying to create a weapon system by using classes and inheriting different scripts from a base one. The problem is that I don’t really know how this works (as I’m learning OOP on the way) and I got an error I don’t really know how to solve.

NullReferenceException: Object reference not set to an instance of an object
Weapon.UseWeapon () (at Assets/Weapon.cs:17)
Shooting.Update () (at Assets/Shooting.cs:23)

I have a BasicGun class where I asign its ammo, ammo used on shot, bullet type and bullet force, but when I try to shoot it throws that error. I noticed that the bullet prefab isn’t instantiating because it is null, but trying to get the prefab still doesn’t work.

Here’s the code:

public class Weapon : MonoBehaviour
{
    protected Shooting player; // class Shooting is from another script, I may change this later so it makes sense

    public int ammo;
    public int ammoRate;
    public GameObject bulletType;
    public float bulletForce;

    public Weapon() {  }

    public void UseWeapon() {
        GameObject bullet = Instantiate(bulletType, player.firePoint.position, player.firePoint.rotation);
        Rigidbody2D rb = bullet.GetComponent<Rigidbody2D>();
        rb.AddForce(player.firePoint.up * bulletForce, ForceMode2D.Impulse);
        ammo -= ammoRate;
    }
}

public class BasicGun : Weapon
{

    private void Awake()
    {
        bulletType = GetComponent<GameObject>();
    }
    public BasicGun()
    {
        ammo = 5;
        ammoRate = 1;
        bulletForce = 45f;
    }
}

And here’s part of the code on the Shooting class

public Weapon currentWeapon;

private void Start()
    {
        currentWeapon = gameObject.AddComponent<BasicGun>();
    }

void Update()
    {
       // Debug.Log(currentWeapon == null);
        HandleMouse();
        if (Input.GetButtonDown("Fire1") && currentWeapon.ammo > 0) currentWeapon.UseWeapon();
    }

6790637--786788--prefab_error_unity.png

Can anyone help me?

2

What’s on line 17 of Weapon.cs? That’s where the error is being thrown.

3

This

GameObject bullet = Instantiate(bulletType, player.firePoint.position, player.firePoint.rotation);

I skipped the first 3 lines “using …” so that didn’t count.
Also, line 23 on Shooting.cs is:

if (Input.GetButtonDown("Fire1") && currentWeapon.ammo > 0) currentWeapon.UseWeapon();
4

I’m guessing from your description it is the Instantiate line which is failing (whatever line 17 is). Where exactly are you assigning the reference to “player”?

But how you troubleshoot null reference errors is always the same:

  1. Go to the line the error refers to
  2. Find all references used on that line
  3. If more than 1 reference used, then before that line check each reference whether it is null
  4. Now that you know which specific reference is null, now go figure out why you’re not assigning a reference to it before trying to use it.
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5

Seems like either player is null or player.firePoint is null. It doesn’t seem like you assign a value to player anywhere so seems likely to be that.

To fix this exception - figure out what is null. Then figure out why it’s null and fix it.

2 Likes
6

As Praetor points out above, the answer is always the same… ALWAYS. It is the single most common error ever. Don’t waste your life on this problem. Instead, learn how to fix it fast… it’s EASY!!

Some notes on how to fix a NullReferenceException error in Unity3D

  • also known as: Unassigned Reference Exception
  • also known as: Missing Reference Exception

http://plbm.com/?p=221

The basic steps outlined above are:

  • Identify what is null
  • Identify why it is null
  • Fix that.

Expect to see this error a LOT. It’s easily the most common thing to do when working. Learn how to fix it rapidly. It’s easy. See the above link for more tips.

This is the kind of mindset and thinking process you need to bring to this problem:

https://discussions.unity.com/t/814091/4

Step by step, break it down, find the problem.

1 Like