How do I fix "object reference not set to an instance of an object" error in unity?

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I was making a game, basically an angry bird rip-off. This is the coding- the error was- object reference not set to an instance of an object

What I have tried:

Here is the coding-

C#

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

public class Birds : MonoBehaviour
{
    Vector2 _startPosition;
    Rigidbody2D _rigidbody2D;
    SpriteRenderer _spriteRenderer;
    void awake()
    {
        _rigidbody2D = GetComponent<rigidbody2d>();
        _spriteRenderer = GetComponent<spriterenderer>();
    }
    // Start is called before the first frame update
    void Start()
    {
        _startPosition = _rigidbody2D.position;
        _rigidbody2D.isKinematic = true;
    }

    void OnMouseDown()
    {
        _spriteRenderer.color = Color.red;
    }   

    void OnMouseUp()
    {
        var currentPosition = GetComponent<rigidbody2d>().position;
        Vector2 direction = _startPosition - currentPosition;
        direction.Normalize();

        _rigidbody2D.isKinematic = false;
        _rigidbody2D.AddForce(direction * 750);

        _spriteRenderer.color = Color.white;
    }

    void OnMouseDrag()
    {
        Vector3 mousePosition = Camera.main.ScreenToWorldPoint(Input.mousePosition);
        transform.position = new Vector3 (mousePosition.x, mousePosition.y, transform.position.z);
    }

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

Posted 11-Aug-21 4:52am

Atharv Goyal

Updated 11-Aug-21 5:36am

PIEBALDconsult

v2

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Richard MacCutchan 11-Aug-21 11:01am

It means that somewhere in your code you are trying to use a variable reference that has never been initialised. But since you did not point out where the error occurs we cannot tell you which one is the offender.

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OriginalGriff · Answer 1 · 2021-08-11T05:27:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterday's shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, it will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, the debugger will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!

Patrice T · Answer 2 · 2021-08-11T05:36:00

Quote:
How do I fix "object reference not set to an instance of an object" error in unity?

Giving complete error message is a good idea because if you dare to read it carefully, it tells you where is the error, and that help to locate the problem.

Quote:
"object reference not set to an instance of an object"

No matter what is the exact problem, somewhere in your code, you try to use a variable that is supposed to be an object.
Either you forgot to initialize the object, either some code failed to return an expected object.
Sometimes, the fail is do to exhausted limited resource, in this case, you need to check if request succeed or not.

How do I fix "object reference not set to an instance of an object" error in unity?

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