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

Good morning guys, so I wanted to know how to solve this error here:

NullReferenceException: Object reference not set to an instance of an object Shooter Enemy.OnCollisionEnter2D (UnityEngine.Collision2D collisionShooter) (at Assets/Scripts/Sniper Enemy.cs:30)

A guy named Kurt-Dekker always says that for errors like that, it's to identify what's null and then find out why it's null. But how do I identify what is null? Do you have any command for that?

Here is my EnemySniper code:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class InimigoAtirador : MonoBehaviour
6. {
7.     public int VidaInimigoAtirador;
8.  
9.     public GameObject MuniçaoPlayer;
10.     private Munição muniçaoplayer;
11.  
12.     public Transform Player;
13.  
14.     void Start()
15.     {
16.         muniçaoplayer = MuniçaoPlayer.GetComponent<Munição>();
17.     }
18.  
19.     void Update()
20.     {
21.         Vector3 dir = Player.position - transform.position;
22.         float angle = Mathf.Atan2(dir.y,dir.x) * Mathf.Rad2Deg;
23.         transform.rotation = Quaternion.AngleAxis(angle -90, Vector3.forward);
24.     }
25.  
26.     void OnCollisionEnter2D(Collision2D collisionAtirador)
27.     {
28.         if(collisionAtirador.gameObject.CompareTag("Muniçao"))
29.         {
30.             VidaInimigoAtirador -= muniçaoplayer.Dano;
31.         }
32.     }
33. }

Thank you very much in advance

 

Based on your question I'd recommend reading this at the very least: https://docs.unity3d.com/Manual/ManagedCodeDebugging.html

What you need to do is place breakpoints, attach your IDE to the unity editor & then check the values of your variables.

 

What is the attribution code?

 

ok, i will give it a read

 

How do I assign the "muniçãoplayer"? Sorry I'm using Google Translate.