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Chapter 7 page 183 (NullReferenceException: Object reference not set to an instance of an object Gun.fireBullet () (at Assets/Scripts/Gun.cs:17))

I have just finished page 182 in the book

I am trying to test the game and I am getting an error in Unity

it runs until I shoot then it stops and produces the following error

NullReferenceException: Object reference not set to an instance of an object
Gun.fireBullet () (at Assets/Scripts/Gun.cs:17)

I have checked my code against the code that I downloaded to accompany the book and it’s the same.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Gun : MonoBehaviour {

public GameObject bulletPrefab;
public Transform launchPosition;
public bool isUpgraded;
public float upgradeTime = 10.0f;

private float currentTime;
private AudioSource audioSource;

void fireBullet() {
Rigidbody bullet = createBullet();
bullet.velocity = transform.parent.forward * 100;
if (isUpgraded) {
Rigidbody bullet2 = createBullet();
bullet2.velocity = (transform.right + transform.forward / 0.5f) * 100;
Rigidbody bullet3 = createBullet();
bullet3.velocity = ((transform.right * -1) + transform.forward / 0.5f) * 100;
if (isUpgraded) {
} else {

public void UpgradeGun() {
isUpgraded = true;
currentTime = 0;

// Use this for initialization
void Start () {
audioSource = GetComponent();

// Update is called once per frame
void Update () {
if (Input.GetMouseButtonDown(0)) {
  if (!IsInvoking("fireBullet")) {
    InvokeRepeating("fireBullet", 0f, 0.1f);
if (Input.GetMouseButtonUp(0)) {
currentTime += Time.deltaTime;
if (currentTime > upgradeTime && isUpgraded == true) {
  isUpgraded = false;


private Rigidbody createBullet() {
GameObject bullet = Instantiate(bulletPrefab) as GameObject;
bullet.transform.position = launchPosition.position;
return bullet.GetComponent();


@vegetarianzombie Do you have any feedback on this? Thank you - much appreciated! :]

using version 2017.1.1f1 ( plus version ) on Mac

I loaded the final chapter code for chapter 7 and that was fine.

I doubled checked my code and started again from the beginning of chapter 7 but I am still getting the issue,

I hope these extra details help.

Hey there, without seeing your project, my guess is that the bullet prefab hasn’t been set in the project. Back in Unity, check the BobbleMarine-Body and look at the Gun component. Check to see if there is a projectile in the Bullet Prefab field.

My guess is that it is missing and that’s the reason you are getting the null exceptions. Let me know how it turns out.


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