Other NullReferenceExceptions when trying to play audio file

So i am making 2d platformer and adding audio to the game when i add the code to play the audio and try to play the audio in the game i get NullReferenceExceptions on the line where the soundManager plays the sound here's the code for player attacking where it plays a fireball sound.

Code (CSharp):

1. using UnityEngine;
2.  
3. public class PlayerAttack : MonoBehaviour
4. {
5.     [SerializeField] private float attackCooldown;
6.     [SerializeField] private Transform firePoint;
7.     [SerializeField] private GameObject[] fireballs;
8.     [SerializeField] private AudioClip fireballSound;
9.  
10.     private Animator anim;
11.     private PlayerMovement playerMovement;
12.     private float cooldownTimer = Mathf.Infinity;
13.  
14.     private void Awake()
15.     {
16.         anim = GetComponent<Animator>();
17.         playerMovement = GetComponent<PlayerMovement>();
18.     }
19.  
20.     private void Update()
21.     {
22.         if (Input.GetMouseButton(0) && cooldownTimer > attackCooldown && playerMovement.canAttack())
23.             Attack();
24.  
25.         cooldownTimer += Time.deltaTime;
26.     }
27.  
28.     private void Attack()
29.     {
30.         SoundManager.instance.PlaySound(fireballSound);
31.         anim.SetTrigger("attack");
32.         cooldownTimer = 0;
33.  
34.         fireballs[FindFireball()].transform.position = firePoint.position;
35.         fireballs[FindFireball()].GetComponent<Projectile>().SetDirection(Mathf.Sign(transform.localScale.x));
36.     }
37.     private int FindFireball()
38.     {
39.         for (int i = 0; i < fireballs.Length; i++)
40.         {
41.             if (!fireballs[i].activeInHierarchy)
42.                 return i;
43.         }
44.         return 0;
45.     }
46. }

and here is the sound manager code

Code (CSharp):

1. using UnityEngine;
2.  
3. public class SoundManager : MonoBehaviour
4. {
5.     public static SoundManager instance { get; private set; }
6.     private AudioSource source;
7.  
8.     private void Awake()
9.     {
10.  
11.         source = GetComponent<AudioSource>();
12.  
13.         //Keep this object even when we go to new scene
14.         if (instance == null)
15.         {
16.             instance = this;
17.             DontDestroyOnLoad(gameObject);
18.         }
19.         //Destroy duplicate gameobjects
20.         else if (instance != null && instance != this)
21.             Destroy(gameObject);
22.     }
23.     public void PlaySound(AudioClip _sound)
24.     {
25.         source.PlayOneShot(_sound);
26.     }
27. [INDENT]}

[/INDENT]

 

The answer is always the same... ALWAYS.

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:
- Identify what is null <-- any other action taken before this step is WASTED TIME
- Identify why it is null
- Fix that

 

With a null ref error, the rules are always the same.

1. Find out what is null
2. Find out why it's null
3. Fix it.

That being said, if you're having trouble with these steps, posting the error so we can see exactly what line it points to can help us to help you.

If your error occurs here, then source is probably null as I assume you aren't passing in a null AudioClip

Code (CSharp):

1. public void PlaySound(AudioClip _sound)
2.     {
3.         source.PlayOneShot(_sound);
4.     }

 

for desription on the error here is a description of the error in terms of the player attack script

 

Code (CSharp):

1. SoundManager.instance.PlaySound(fireballSound);

This is the line your error points to. So break it apart. @MelvMay mentioned understanding the difference between a value and reference type. Once broken apart, you'll know that SoundManager and PlaySound can't be null because they aren't variables. Which leaves two options.

 

i found a report from Microsoft's website on the difference between the 2 which it says .There are two kinds of types in C#: reference types and value types. Variables of reference types store references to their data (objects), while variables of value types directly contain their data. With reference types, two variables can reference the same object; therefore, operations on one variable can affect the object referenced by the other variable. With value types, each variable has its own copy of the data, and it's not possible for operations on one variable to affect the other (except in the case of in, ref, and out parameter variables; see in, ref, and out parameter modifier). this would be the difference between the 2 types correct?

 

You're overcomplicating this for yourself. A null exception means that something is null when it's not supposed to be null. For the line the console is pointing you to there are two possible sources:

SoundManager.instance

and

fireballSound

.

To find the problem you need to insert Debug.Log lines directly before the line that is causing the error. If either of these lines says "true" then it's null.

Code (csharp):

1. Debug.Log($"SoundManager.instance: {SoundManager.instance == null}");
2. Debug.Log($"fireballSound: {fireballSound == null}");
3. SoundManager.instance.PlaySound(fireballSound);

 

This is not part of the three steps. It won't be helpful to you. I'm not kidding.

How to fix a NullReferenceException error

https://forum.unity.com/threads/how-to-fix-a-nullreferenceexception-error.1230297/

Three steps to success:
- Identify what is null <-- any other action taken before this step is WASTED TIME
- Identify why it is null
- Fix that