Scripts Works on one scene but error in another

Question

So I'm getting an error which says

Object reference not set to an instance of an object Explode.LateUpdate () (at Assets/Scripts/Explode.cs:40)

I'm not sure why I get this error as everything works fine and I have the exact same script in a different scene without the error message. I'd love any help please.

I'm exploding my player with different coloured boxes.

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

    public class Explode : MonoBehaviour {

        [System.Serializable]
        public class ExplodeColours
        {
            public Color32[] Colours;
        }


        public static bool explode, explodeOnce;
        public ParticleSystem Explodes;
        private ParticleSystem explosionSystem;
        public Transform player;
        public List<ExplodeColours> ColoursList;

        // Use this for initialization
        void Start () {
            PlayerPrefs.SetInt("SelectedChar", 0);
            PlayerPrefs.Save();
            explodeOnce = false;
            explode = false;
        }

        // Update is called once per frame
        void Update () {
            if (explode == true)
            {
                explodeOnce = true;
                PlayerExplode();
            }
        }
        void LateUpdate()
        {
            if (explode)
            {
                ParticleSystem.Particle[] Particles = new ParticleSystem.Particle[explosionSystem.main.maxParticles];
                //ParticleSystem.Particle[] Particles = new ParticleSystem.Particle[Explodes.main.maxParticles];
                int NumParticlesAlive = explosionSystem.GetParticles(Particles);
                for (int i = 0; i < NumParticlesAlive; i++)
                {
                    Particles[i].startColor = (ColoursList[PlayerPrefs.GetInt("SelectedChar")].Colours[Random.Range(0, ColoursList[PlayerPrefs.GetInt("SelectedChar")].Colours.Length)]);
                }
                explosionSystem.SetParticles(Particles, NumParticlesAlive);
                explode = false;
            }

        }
        void PlayerExplode()
        {
            explosionSystem = Instantiate(Explodes, player.position, player.rotation);
            explosionSystem.Play();
        }
    }

Your error is on line 40 as the message say, make sure everything that is called is instantiated in this line. — S.Fragkos, Apr 20 '18 at 06:37

score 2 · Accepted Answer · edited Apr 20 '18 at 13:24

If this is line 40 (I had to count):

ParticleSystem.Particle[] Particles = new ParticleSystem.Particle[explosionSystem.main.maxParticles];

Then explosionSystem or main or maxParticles is null. I'm going to close this as a duplicate, this error is so common and the way to resolve it is easy.

But a break point on the line of code, when the code control halts, check which object is null and make sure its set.

EDIT:

Use the GetComponent to initialize the explosionSystem variable in the Start function.First, find the GameObject the ParticleSystem is attached to the use GetComponent to get the ParticleSystem.

private ParticleSystem explosionSystem;
void Start()
{
    GameObject obj = GameObject.Find("NameOfObjectParticleSystemIsAttachedTo");
    explosionSystem = obj.GetComponent<ParticleSystem>();
}

Also, inside the for loop, you tried to use Particles's startColor property without initializing each one. You can do that with Particles[i] = new ParticleSystem.Particle();.

Change:

for (int i = 0; i < NumParticlesAlive; i++)
{
    Particles[i].startColor 
 = (ColoursList[PlayerPrefs.GetInt("SelectedChar")].Colours[Random.Range(0, ColoursList[PlayerPrefs.GetInt("SelectedChar")].Colours.Length)]);
}

to

for (int i = 0; i < NumParticlesAlive; i++)
{
    Particles[i] = new ParticleSystem.Particle();
    Particles[i].startColor 
 = (ColoursList[PlayerPrefs.GetInt("SelectedChar")].Colours[Random.Range(0, ColoursList[PlayerPrefs.GetInt("SelectedChar")].Colours.Length)]);
}

Thanks for your reply and yes I know this is a common error but the script works fine in one scene and I get an error in another. Everything that I can see is set so I can't see why it won't work. — Toby Langdon, Apr 20 '18 at 07:34
Please, please, please do yourself a huge favour and learn how to debug code. Your `explosionSystem` is null. You need to work out why it wasn't instantiated. We can't do this for you without all the source code. Watch some debugging videos. This is a good/easy problem to learn debugging to solve: put the code in a try catch, put a breakpoint on the Catch, when the exception occurs, hover your mouse over the variables making sure everything is set. You've missed something. Ps If I reopened this you'll likely get downvotes and then someone else will close it as a duplicate anyway. — Jeremy Thompson, Apr 20 '18 at 08:29
I @Jeremy and Toby, I have modified to add here OP has messed up and the fix. Hopefully, your problem is solved. — Programmer, Apr 20 '18 at 13:20

score 0 · Answer 2 · answered Apr 20 '18 at 06:40

0

To avoid the null reference error, make sure all variables (which are using) has values other wise at least assign default values in constructor level

answered Apr 20 '18 at 06:40

Chandrashekar Jupalli

337
3
15

Scripts Works on one scene but error in another

2 Answers2