Destroy all object with tag

Unity Engine
1

Hi,

I’m new to unity and programming and i’m trying to make a simple game and I’m stuck.

I have a player object that collides with an enemy object, and both destroys, so far so good.

But the problem is that I want all of the spawned enemies to be destroyed if one of them collides with the player.

The enemy objects has a tag = enemy, and are prefab clones.

Here is my code that is attached to the player:

using UnityEngine;
using System.Collections;

public class DestroyByContact : MonoBehaviour
{
    public GameObject explosion;
    private GameController gameController;

   
    void Start ()
    {
        GameObject gameControllerObject = GameObject.FindWithTag ("GameController");
        if (gameControllerObject != null)
        {
            gameController = gameControllerObject.GetComponent <GameController>();
        }
        if (gameController == null)
        {
            Debug.Log ("Cannot find 'GameController' script");
        }
    }

   
    void OnTriggerEnter(Collider other)
    {
        if (other.tag == "Boundary")
        {
            return;
        }

   

        Instantiate(explosion, transform.position, transform.rotation);
        Instantiate(explosion, other.transform.position, other.transform.rotation);

        Destroy(other.gameObject); //Enemy that collided, but want all enemies destroyed.
        Destroy(gameObject); //Player


        gameController.GameOver ();

    }


}
2 
GameObject[] enemies = GameObject.FindGameObjectsWithTag("Enemy");
foreach(GameObject enemy in enemies)
  GameObject.Destroy(enemy);
1 Like
3

@ThomasCreate 's solution would work!

Alternatively, and I think ideally, you should avoid having to “Find” GameObjects in a scene hierarchy. Instead, for any such purpose, you should hold references of such spawn-able entities somewhere in your code separately.

A way to go about your situation could be that

  1. You declare a static System.Action in your Enemy component attached to each enemy gameobject
  2. Send out an enemy’s own reference to the action in Start() method of your Enemy class
  3. Have A class, say GameLogic, contain the action definition for your enemies. So in this class, you could keep a list of all enemies
  4. On collision with an enemy, tell the GameLogic to destroy gameobjects associated with all enemies.
4

FindObjectsWithTag() is very fast though (much faster than regular GameObject.Find()), and he only has to call it once; it’s not like it’s done every frame. The extra bookkeeping required to manually keep a reference to all enemies will not pay off, and it only serves to make the code more complex.

I wouldn’t be surprised if the tag system basically is doing what you are suggesting, but built-in.

5

Thank you for your help :slight_smile:
I have only two more questions about my problem.

The code worked, but not all the objects were destroyed.
For example:
I have a hazard of 10 enemies moving towards the player.
Five enemies is visible in the scene when my player collide with one of them and all 5 destroys thanks to the new code, but the five that hasn’t yet arrived into the scene aren’t destroyed. I hope you understand what I mean :slight_smile:

Second question,
Is it possible to make all of the enemies explode with Instantiate like the player and the enemy that collided?

6

FindObjectsWithTag() is way faster than GameObject.Find(), agreed! It also keeps a list of all gameobjects with a specific tag. But generally, simple arrays are the fastest, followed by Lists and then FindObjectsWithTag().

@off112 … If the other 5 enemies spawn after the collision, they would obviously not get destroyed. The logic that destroyed them is already in the past. I hope you understand what I mean :wink:

I don’t really get your second question.

1 Like
7

OK, I think I understand.

I’ll hope I can explain my second question better. If you look at my code above, that I trigger an explosion with Instantiate when the player collide with an enemy. But it’s only the enemy that collides that will explode. I would like that all the enemies explodes.

8

Just instantiate explosions at the enemy positions in the foreach loop that destroys them. :wink:

9
  1. Place “Enemy” script on each enemy object.
  2. Write “OnDestroy” method in Enemy class and instantiate an explosion gameobject inside it at the current position. Something like this:
 public class Enemy : Monobehavior
{
        void OnDestroy()
        {
                Instantiate(Resources.Load("EXPLOSION_PREFAB_PATH"), transform.position, Quaternion.identity)
        }
}

I haven’t tested the code for any spelling mistakes, so maybe you should.

1 Like