Collision.gameobject.getcomponent not working?

Unity Engine
,
1

Hi this code below is not working having the
NullReferenceException: Object reference not set to an instance of an object
error. How can i make it work script is MonoBehaviour?

Not working part

            collision.gameObject.GetComponent<EnemyHealthBar>().TakeDamage(20);

full code

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Bullet : MonoBehaviour
{
    //Rigidbody mermiRB;
    //EnemyHealthBar enemyHBSC;

    // Start is called before the first frame update
    void Start()
    {
        //mermiRB = GetComponent<Rigidbody>();
        //enemyHBSC = GameObject.FindObjectOfType<EnemyHealthBar>();
    }

    // Update is called once per frame
    void Update()
    {
    }

    private void OnCollisionEnter(Collision collision)
    {
        if (collision.gameObject.tag == "Enemy")
        {
            collision.gameObject.GetComponent<EnemyHealthBar>().TakeDamage(20);
            //enemyHBSC.TakeDamage(10);
            Destroy(gameObject);
        }

        if (collision.gameObject.tag =="Block")
        {
            Destroy(gameObject, 1f);
        }
    }
}
2

If you have more than one or two dots (.) in a single statement, you’re just being mean to yourself.

How to break down hairy lines of code:

http://plbm.com/?p=248

Break it up, practice social distancing in your code, one thing per line please.

“Programming is hard enough without making it harder for ourselves.” - angrypenguin on Unity3D forums

I assure you that GetComponent() didn’t stop working.

1 Like
3

Thanks when i try like in the example you send me i saw the problem really fast. The script was in the child of my game object thats why i couldnt acces it. I understand that because of example codes debug.log.

Code is working now but not like i want it.
new code btw;

        if (collision.gameObject.tag == "Enemy")
        {
            GameObject enemyObject = GameObject.FindWithTag("Enemy");
            if (enemyObject == null)
            {
                Debug.Log("FindWithTag returned null for Player tag");
            }
            EnemyHealthBar enemyHBSC = enemyObject.GetComponentInChildren<EnemyHealthBar>();
            if (enemyHBSC == null)
            {
                Debug.Log("playerObject.GetComponent returned null");
            }
            enemyHBSC.TakeDamage(40);
        }

but the problem player shoot enemy but change the health of other. 2 enemys have same script shoot not changing
the collided one changing the other

8241009--1077663--upload_2022-6-29_16-47-38.png

4

Sounds like either you have a static health variable, or perhaps something else is going on.

Here is how you can find out!!

What is often happening in these cases is one of the following:

  • the code you think is executing is not actually executing at all
  • the code is executing far EARLIER or LATER than you think
  • the code is executing far LESS OFTEN than you think
  • the code is executing far MORE OFTEN than you think
  • the code is executing on another GameObject than you think it is
  • you’re getting an error or warning and you haven’t noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling Debug.Log() statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

  • is this code even running? which parts are running? how often does it run? what order does it run in?
  • what are the values of the variables involved? Are they initialized? Are the values reasonable?
  • are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer or iOS: https://discussions.unity.com/t/700551 or this answer for Android: https://discussions.unity.com/t/699654

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here’s an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://discussions.unity.com/t/839300/3

You must find a way to get the information you need in order to reason about what the problem is.

1 Like
5

Why are you doing this: GameObject enemyObject = GameObject.FindWithTag("Enemy"); when you already know which gameobject you are colliding with? You are effectively ignoring the object you have collided with and told Unity to just get you the first gameobject that it can find with the Enemy tag.
What happens if you change that line to this: GameObject enemyObject = collision.gameObject;
That should make it just refer to the object that the collision is happening with.