Global Variables & Object reference not set to an instance of an object

Questions & Answers
1

Hi… I need your help

I have a script “GameControl” and a script “SecurityCamera”.

SecurityCamera checks if the player is seen by the camera and calls alarm. Alarm should be a game ending event and restart the level.

In GameControl I want to store variables and functions used by multiple things.

GameControl Script:

    public class GameControl : MonoBehaviour {
        public static GameControl control;
        public void Respawn() {Code Stuff}
}

SecurityCamer Script:

void OnTriggerEnter(Collider other)
    {
        if (!other.CompareTag("Player"))
            return;
        GameControl.control.Respawn();
    }

Now I have the problem that this gives me the error:

NullReferenceException: Object
reference not set to an instance of an
object EnemyCamera.OnTriggerEnter
(UnityEngine.Collider other) (at
Assets/EnemyCamera.cs:47)

(double clicking it marks “GameControl.control.Respawn();” in my IDE)

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I looked it up in my old files, where I once did the same and it worked.

Exactly the same script for “GameControl”.

Only difference: how I call it

void Start () {
Save.onClick.AddListener(() => { GameControl.control.Save(); });
Load.onClick.AddListener(() => { GameControl.control.Load(); });
}

----------------------------------------------------------------------------

So why is this happening now? How can I fix it?

3

If the player is spawned inside the security camera trigger when the level starts, then it’s probably because GameControl.control hasn’t been yet set (I suppose you’re setting it in GameControl.Awake or GameControl.Start).

2

You don’t need the static variable (public static GameControl control;) INSIDE the GameControl script itself. Get rid of it.

In your SecurityCamera script you can add a reference to your GameControl script.

private GameControl gameControlScript = new GameControl():

Then you just call that reference in the code.

void OnTriggerEnter(Collider other)
     {
         if (!other.CompareTag("Player"))
             return;
         gameControlScript.Respawn();
     }