Error in Chapter 3 page 84 tranform.parent not working

đź“š Official Books Unity Games by Tutorials
1

Hello,
Problematic part of code:

bullet.GetComponent().velocity = transform.parent.forward * 100;

When i launch game and start to fire i got error:

NullReferenceException: Object reference not set to an instance of an object
Gun.fireBullet () (at Assets/Scripts/Gun.cs:31)

Here is my all script:

using UnityEngine;
using System.Collections;

public class Gun : MonoBehaviour {

public GameObject bulletPrefab;
public Transform launchPosition;

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
if (Input.GetMouseButtonDown(0)) {
if (!IsInvoking(“fireBullet”)) {
InvokeRepeating(“fireBullet”, 0f, 0.1f);
}
}
if (Input.GetMouseButtonUp(0)) {
CancelInvoke(“fireBullet”);
}
}

void fireBullet() {
GameObject bullet = Instantiate(bulletPrefab) as GameObject;

  bullet.transform.position = launchPosition.position;

  bullet.GetComponent<Rigidbody>().velocity = transform.parent.forward * 100;

}
}

I dont know what I am doing wrong? I have Unity version 5.4.2f2.

I tried some Debug.Log and found, that transform.forward is possible and working corectly. But I dont understand differences. Can someone please explain to me and why is in book transform.parent.forward?

Thank you very much.
Zdenek Hamak

2

Hi h-max,

The first thing we need to determine if there is a rigidbody attached to the bullet prefab. If there isn’t a Rigidbody component, then that’s the cause of the error.

Make sure to check it that component is present. If that GameObject is still in the Hierarchy, select it and if you see a Rigidbody component in the Inspector, click Apply button.

Next, check your Project Browser and find the original prefab. Click on it, and check the Inspector. If you don’t see a rigidbody component, then that’s your problem. Otherwise, something else may be at play.

Let me know how that turns out.

Cheers!
Brian

3

Hi Brian,
thank you for answer and help.
I have rigidbody attached to bullet prefab( name as Projectile ) I make screenshot.

Projectile prefab.png673Ă—729 83.9 KB

I have not Bullet GameObject in Hierarchy. If I take prefab into Hierarchy, GameObject have rigidBody.

I also check SpaceMarine. SpaceMarine-Head and Body have rigidBody but SpaceMarine havent( I checked it with book and it should be correct). Gun script has attached Projectil into Bullet Prefab.
Here is screen:

Thank you,
Zdenek

4

I am getting exact same error at same code too…please help

5

@h-max @kunal1784

I think the problem comes from this part:

transform.parent.forward * 100

When you instantiate a bullet using this code:

GameObject bullet = Instantiate(bulletPrefab) as GameObject;
bullet.transform.position = launchPosition.position;

The GameObject might have no parent it can get its forward direction from, so it throws a nullreference error.
Try replacing:

transform.parent.forward * 100

With:

transform.forward * 100

Let me know if that works.

Cheers!

6

Thanks a lot, now it worked fine…

7

I have another problem now…when space marine dies, the bullets won’t stop…his dying body still keeps shooting with the gun…please help

8

Hi, this solution worked great for the nullreference error, but the space marine will not stop shooting when i release the mouse button. Do you have any idea what is causing this?