C# Need Help Finding Where Null Reference Exception Is

Questions & Answers
1

I have a script that generates a rope down the y axis. For some reason I’m getting a null reference exception and I can’t figure out where it’s coming from. When I click on it sends me to random lines on my code. Any help would be appreciated.

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
public class RopeController : MonoBehaviour
{
	public GameObject fragmentPrefab;
	
	public  List<GameObject> fragments = new List<GameObject>();
	private Vector3 interval = new Vector3(0f, -0.5f, 0f);

	private float[] xPositions;
	private float[] yPositions;
	private float[] zPositions;
	
	private CatmullRomSpline splineX;
	private CatmullRomSpline splineY;
	private CatmullRomSpline splineZ;
	
	private int splineFactor = 4;
	
	void Start()
	{

	}
	
	void Update()
	{
		Vector3 position = transform.position;
		
		for (int i = 0; i < (int)gameObject.transform.position.y; i++) {
		if(fragments.Count <= (int)gameObject.transform.position.y){
			fragments.Add(null);
			fragments *= (GameObject) Instantiate(fragmentPrefab, position, Quaternion.identity);*

_ fragments*.transform.parent = transform;*_

_ SpringJoint joint = fragments*.GetComponent();
 if (i > 0) {
 joint.connectedBody = fragments[i - 1].rigidbody;
 }*_

* position += interval;*
* }*
* }*

* LineRenderer renderer = GetComponent();*
_ renderer.SetVertexCount((fragments.Count - 1) * splineFactor + 1);_

* xPositions = new float[fragments.Count];*
* yPositions = new float[fragments.Count];*
* zPositions = new float[fragments.Count];*

* splineX = new CatmullRomSpline(xPositions);*
* splineY = new CatmullRomSpline(yPositions);*
* splineZ = new CatmullRomSpline(zPositions);*

* float activeFragmentNum = (float)fragments.Count;*
_ float vy = Input.GetAxisRaw(“Vertical”) * 20f * Time.deltaTime;
* activeFragmentNum = Mathf.Clamp(activeFragmentNum + vy, 0, fragments.Count);*_

* for (int i = 0; i < fragments.Count; i++) {*
* if (i <= fragments.Count - activeFragmentNum) {*
_ fragments*.rigidbody.position = transform.position;
fragments.rigidbody.isKinematic = true;
} else {
fragments.rigidbody.isKinematic = false;
}
}
}*_

* void LateUpdate()*
* {*
* LineRenderer renderer = GetComponent();*

* for (int i = 0; i < fragments.Count; i++) {*
_ Vector3 position = fragments*.transform.position;
xPositions = position.x;
yPositions = position.y;
zPositions = position.z;
}*_

_ for (int i = 0; i < (fragments.Count - 1) * splineFactor + 1; i++) {
* renderer.SetPosition(i, new Vector3(
splineX.GetValue(i / (float) splineFactor),
splineY.GetValue(i / (float) splineFactor),
splineZ.GetValue(i / (float) splineFactor)));
}
}
}*_

2

you set some parameters as public,(fragmentPrefab…)
go to the inspector for that script, check if you have assigned the public parameters.

Tamir.

3

You have error, because your logic in loop “for” is not correct. You write:

 for (int i = 0; i < (int)gameObject.transform.position.y; i++) {
  if(fragments.Count <= (int)gameObject.transform.position.y){
   fragments.Add(null);
    fragments *= ...*

For, example, List of fragments is not empty (for example, have 5 elements). Then in condition “if” (for i == 0) you add null object. Last object have index 5, but you work with index 0. I think, you must modify last element of List. Try this:
void Update() {
Vector3 position = transform.position;

for (int i = 0; i < (int)gameObject.transform.position.y; i++) {
if(fragments.Count <= (int)gameObject.transform.position.y){
fragments.Add(null);
//Use not “i”, but last index
fragments[fragments.Count-1] = (GameObject) Instantiate(fragmentPrefab, position, Quaternion.identity);
fragments[fragments.Count-1].transform.parent = transform;

SpringJoint joint = fragments[fragments.Count-1].GetComponent();
if (fragments.Count-1 > 0) {
//Connect to prelast element
joint.connectedBody = fragments[fragments.Count - 2].rigidbody;
}

position += interval;
}
}
//Not use names matches with method, change “renderer” on “myrenderer”
LineRenderer myrenderer = GetComponent();
//Check counts:
if(fragments.Count > 0) {
myrenderer.SetVertexCount((fragments.Count - 1) * splineFactor + 1);
//Not correct index, for example list have 7 elements (Count), but last index is 6
xPositions = new float[fragments.Count - 1];
yPositions = new float[fragments.Count - 1];
zPositions = new float[fragments.Count - 1];

splineX = new CatmullRomSpline(xPositions);
splineY = new CatmullRomSpline(yPositions);
splineZ = new CatmullRomSpline(zPositions);

float activeFragmentNum = (float)fragments.Count;
float vy = Input.GetAxisRaw(“Vertical”) * 20f * Time.deltaTime;
activeFragmentNum = Mathf.Clamp(activeFragmentNum + vy, 0, fragments.Count);

for (int i = 0; i < fragments.Count; i++) {
if (i <= fragments.Count - activeFragmentNum) {
fragments*.rigidbody.position = transform.position;*
fragments*.rigidbody.isKinematic = true;*
} else {
fragments*.rigidbody.isKinematic = false;*
}
}
}
}
In LateUpdate() changing name LineRenderer too. I hope that it will help you.