NullReferenceException: Object reference not set to an instance of an object

Unity Engine
1

please help… T_T

i am new making game, and this is my first time try to make game such a ball. i find error null exception for this code, and i dont know why

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

public class BallController : MonoBehaviour
{
[SerializeField]
private float speed;

Rigidbody rb;

void awake()
{
rb = GetComponent ();
}
// Start is called before the first frame update
void Start()
{

rb.velocity = new Vector3 (speed, 0, 0);
}

// Update is called once per frame
void Update()
{

}
}

7396760--903419--my code.png
7396760--903419--my code.png1161×434 44.2 KB

2

Did you attach a rigidbody to the gameobject with this script? If yes, then paste the line the error log takes you to.

This error happens when you try to access something that is still null. If you don’t have a rigidbody, it’ll return null.

3

Fortunately it does not matter what you are doing.

The answer is always the same… ALWAYS. It is the single most common error ever.

Don’t waste your life spinning around and round on this error. 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
  • also known as: Object reference not set to an instance of an object

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.

You need to figure out HOW that variable is supposed to get its initial value. There are many ways in Unity. In order of likelihood, it might be ONE of the following:

  • drag it in using the inspector
  • code inside this script initializes it
  • some OTHER external code initializes it
  • ? something else?

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.

Here is a clean analogy of the actual underlying problem of a null reference exception:

https://discussions.unity.com/t/840647/7

1 Like
4

As above but also you need to be more careful and use the EXACT case for things as C# is case-sensitive. The method you want is this (note the case): Awake

2 Likes
5

Oh nice spot … OP, pay close attention to this ^ ^ ^ ^

How to do tutorials properly:

Tutorials are a GREAT idea. Tutorials should be used this way:

Step 1. Follow the tutorial and do every single step of the tutorial 100% precisely the way it is shown. Even the slightest deviation (even a single character!) generally ends in disaster. That’s how software engineering works. Every single letter must be spelled, capitalized, punctuated and spaced (or not spaced) properly. Fortunately this is the easiest part to get right. Be a robot. Don’t make any mistakes. BE PERFECT IN EVERYTHING YOU DO HERE.

If you get any errors, learn how to read the error code and fix it. Google is your friend here. Do NOT continue until you fix the error. The error will probably be somewhere near the parenthesis numbers (line and character position) in the file. It is almost CERTAINLY your typo causing the error, so look again and fix it.

Step 2. Go back and work through every part of the tutorial again, and this time explain it to your doggie. See how I am doing that in my avatar picture? If you have no dog, explain it to your house plant. If you are unable to explain any part of it, STOP. DO NOT PROCEED. Now go learn how that part works. Read the documentation on the functions involved. Go back to the tutorial and try to figure out WHY they did that. This is the part that takes a LOT of time when you are new. It might take days or weeks to work through a single 5-minute tutorial. Stick with it. You will learn.

Step 2 is the part everybody seems to miss. Without Step 2 you are simply a code-typing monkey and outside of the specific tutorial you did, you will be completely lost.

Of course, all this presupposes no errors in the tutorial. For certain tutorial makers (like Unity, Brackeys, Imphenzia, Sebastian Lague) this is usually the case. For some other less-well-known content creators, this is less true. Read the comments on the video: did anyone have issues like you did? If there’s an error, you will NEVER be the first guy to find it.

Beyond that, Step 3, 4, 5 and 6 become easy because you already understand!

1 Like