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Question by Skalde · Mar 31, 2013 at 12:00 AM · errornullreferenceexception

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

alt textalt text

I'v been following the BurgZergArcade tutorials and came across this error: NullReferenceException: Object reference not set to an instance of an object

In these Following lines:

eh.AddjustCurrentHealth(-10);

Attack();

I really hope anyone can help cause i'm lost at this. Heres my entire "Player Attack" C# Script:

using UnityEngine; using System.Collections;

public class PlayerAttack : MonoBehaviour { public GameObject target; public float attackTimer; public float coolDown;

 // Use this for initialization
 void Start () {
     attackTimer = 0;
     coolDown = 2.0f;
 }
 
 // Update is called once per frame
 void Update () {
     if(attackTimer > 0)
         attackTimer -= Time.deltaTime;
     
     if(attackTimer < 0)
         attackTimer = 0;
     
     if(Input.GetKeyUp(KeyCode.F)) {
         if(attackTimer == 0) {
             Attack();
             attackTimer = coolDown;
         }
     }
 
 }
 
 private void Attack() {
     float distance = Vector3.Distance(target.transform.position, transform.position);
     
     Vector3 dir = (target.transform.position - transform.position).normalized;
     
     float direction = Vector3.Dot(dir, transform.forward);
     
     if(distance < 2.5f) {
         if(direction > 0) {
             EnemyHealth eh = (EnemyHealth)target.GetComponent("EnemyHealth");
             eh.AddjustCurrentHealth(-10);
         }
     }
 }

}

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Answer by aldonaletto · Mar 31, 2013 at 01:08 AM

Probably the script EnemyHealth was not found in the target object, what assigns a null value to eh and causes this error. Verify whether the target has such script, or add a debug line like this:

      EnemyHealth eh = (EnemyHealth)target.GetComponent("EnemyHealth");
      if (!eh){
          print("EnemyHealth not found");
      } else {
          eh.AddjustCurrentHealth(-10);
      }
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avatar image Skalde · Mar 31, 2013 at 10:23 AM 0
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Hi thx aldonaletto for your advice i'v trieditand as you prodicted it doesnt find the game object.. but how do i make it so??

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Answer by whydoidoit · Mar 31, 2013 at 10:28 AM

  • Make sure that all of the enemies have the EnemyHealth script attached.

  • Ensure that the Attack function cannot be called with a target that is not equipped with an EnemyHealth

  • If attack can only target things with EnemyHealth then change the script to indicate that by defining target as EnemyHealth not GameObject

Also don't do this: (EnemyHealth)target.GetComponent("EnemyHealth");

Do this: target.GetComponent< EnemyHealth>()

It's faster, type safe (less error prone) and less typing!

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avatar image Skalde · Mar 31, 2013 at 11:05 AM 0
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i only have it on a test scene wiith 1 enemy and i has enemy health on it.. i just have no ideer how to make the script find the enemy health, can you give me an example??

avatar image whydoidoit · Mar 31, 2013 at 11:40 AM 0
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Take a screen shot of your Editor window when you have an enemy selected (and the game is running) then post that screen shot by editing your question and another with the player selected

avatar image whydoidoit · Mar 31, 2013 at 11:41 AM 0
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Actually have you set the "target" variable of this attack at all?

avatar image Skalde · Mar 31, 2013 at 11:51 AM 0
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yea i set the target to the Enemy gameobject and i'v tried anything that came in my $$anonymous$$d...

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