Yet another null reference exception

Questions & Answers
1

I have two identical instantiated objects in the game world. They both have the same script in them, and when they collide they both fire off the same error.

void OnTriggerEnter(Collider other) 
	{
		colliderList.Add(other.gameObject);

    }
	void OnTriggerExit(Collider other)
	{
		colliderList.Remove(other.gameObject);
	}

NullReferenceException: Object reference not set to an instance of an object objectCollision.OnTriggerExit (UnityEngine.Collider other)

I need to track(and sometimes modify) each objects colliders, so what am I doing wrong here?

2

Add this to the Start or Awake or OnEnable function of the class.

 colliderList =  new List<GameObject>();

This is needed because, an object needs to be initialized before being used.

and for OnTriggerExit()

void OnTriggerExit(Collider other)
    {
       if(colliderList.Contains(other.gameObject))
            colliderList.Remove(other.gameObject);
    }

This needed because you might have removed the object from list elsewhere in the code or would do that in future. It is safe to check for it always.