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

Questions & Answers
1

hello guys !

i have a game object ( an ennemy) that is instansiated 1 second after the start of the game from a prefab.

with this code

#pragma strict
// this is the object(prefab) i am instantiating
public var zombprefab: Rigidbody;
var ennemies: GameObject[];
private var temps : float = 1f;
public var spawnV : float = 7f;





// this is the position on the scene to wich the zombie spawn
public var spawn: Transform;

function Start () 
{

}

function Update () 
	{
	// after 1 second of entering the game zombies are instantiated on the scene as long as they are less or equal to 10 
	// the instantiation rate define by the variable spawnV is of one zombie every 7 second
	  if(temps < Time.time && ennemies.Length < 10)
			{
			var zombieinstance: Rigidbody;
			zombieinstance = Instantiate(zombprefab, spawn.position, spawn.rotation);
			temps = Time.time + spawnV;
			}
			
		// i keep track of the number of ennemies on the scene by storing their number into the ennemies variable
		ennemies = GameObject.FindGameObjectsWithTag("ennemie");
		
				
			
			
	
	}

that zombie prefab that is istantiated , have a script that i am trying to access like fallow

 #pragma strict
    
        public var jumpspeed = 11f;
    	public var movespeed = 10f;
    	private var robcollider : CapsuleCollider;
    	var anim : tk2dSpriteAnimator;
    	var zombie : ZOMBIE;
    	
    	
    	
    	
    	
    	
    	
    	function Start () {
    	
     anim = GetComponent(tk2dSpriteAnimator);
     robcollider = GetComponent(CapsuleCollider);
// HERE I AM TRYING TO ACCESS THE SCRIPT THAT IS ATTACHED TO THE INSTANTIATED PREFAB
     zombie = GameObject.Find("Zombie").GetComponent(ZOMBIE);
     }

but i receive the fallowing error :
NullReferenceException: Object reference not set to an instance of an object .

i understand it is because i am triying to access the script on the a gameobject that is not yet instantiated at the start of the game.

but my question is , how can i overcome this issue
thanks in advance.

2

If the zombie is spawned 1 second after the game starts, but you want your following script to start following 0 seconds after the game starts… well, I guess you see there is an inconsistency there. What is the follower script supposed to follow from second 0 to second 1?

If your zombie must spawn some time after game start, you have no other choice but make the follower script wait until there is a zombie to follow. Instead of having that last line in the Start() method of the follower script, remove it and have this in Update().

function Update(){
    if(!zombie){
        var zombieObject = GameObject.Find("Zombie");
        if(zombieObject){
            zombie = zombieObject.GetComponent(ZOMBIE);
        }
    }

    if(zombie){
        // Do here the things that this follower script is supposed to do when it has found the zombie...
    }
}