CODEWITHSUNDEEP
c#unity-game-engine
Charlotte Barnekow
Charlotte Barnekow

Reputation: 77

How to activate trigger when gameObjects are destroyed?

I want to activate/enable a TriggerCollider when the enemies in the area are killed. The enemies doesn't come in a certain order so can't add a script to a single enemy. I created an empty game object and attached below (faulty) script. I want do if( the public game objects are destroyed) activate trigger.

Would you know the correct for this?

public class ActivateDialogueTrigger : MonoBehaviour {

    public GameObject DialogueTrigger;

    public GameObject Enemy01;
    public GameObject Enemy02;
    public GameObject Enemy03;
    public GameObject Enemy04;
    public GameObject Enemy05;
    public GameObject Enemy06;

    void Start () {

        DialogueTrigger.SetActive(false);       
    }


    void Update () {
        if(gameobjects.destroyed){

            DialogueTrigger.SetActive(true);
        }
    }
}

Upvotes: 2

Views: 8007

Answers (1)

Hellium
Hellium

Reputation: 7356

I see two options: a "fastidious", but clean one, and a quick, "dirty" and less efficient one.

Using events

You can attach to each of your objects a script responsible for dispatching an event when the object gets destroyed.

public class OnDestroyDispatcher : MonoBehaviour
{
    public event System.Action<GameObject> OnObjectDestroyed ;
    private void OnDestroy()
    {
        if( OnObjectDestroyed != null ) OnObjectDestroyed( gameObject ) ;
    }
}

Then, in your script:

public class ActivateDialogueTrigger : MonoBehaviour
{
    // Drag & drop the objects in the inspector
    public OnDestroyDispatcher[] OnDestroyDispatchers ;

    // You will be able to add a function once all the objects are destroyed
    public UnityEngine.Events.UnityEvent OnAllObjectsDestroyed;
    
    void Start ()
    {
    
        for( int i = 0 ; i < OnDestroyDispatchers.Length ; ++i )
            OnDestroyDispatchers[i].OnObjectDestroyed += OnObjectDestroyed ;
    }
    
    
    private void OnObjectDestroyed (GameObject destroyedObject)
    {

        CheckAllObjectsAreDestroyed();       
    }
    
    
    private void CheckAllObjectsAreDestroyed ()
    {    
        for( int i = 0 ; i < OnDestroyDispatchers.Length ; ++i )
        {
            if( OnDestroyDispatchers[i] != null || OnDestroyDispatchers[i].gameObject != null )
                return ;
        }

        if( OnAllObjectsDestroyed != null )
            OnAllObjectsDestroyed.Invoke() ;       
    }

}

By pooling each frame

After an object is destroyed, an equality check with null will return true. The object is actually not really null but the "==" operator is overloaded so that you can check whether the object has been destroyed.

public class ActivateDialogueTrigger : MonoBehaviour
{
    // Drag & drop the objects in the inspector
    public GammeObject[] YourGameObjects ;

    // You will be able to add a function once all the objects are destroyed
    public UnityEngine.Events.UnityEvent OnAllObjectsDestroyed;
    
    void Update ()
    {
        CheckAllObjectsAreDestroyed();
    }
    
    private void CheckAllObjectsAreDestroyed ()
    {    
        for( int i = 0 ; i < YourGameObjects.Length ; ++i )
        {
            if( YourGameObjects[i] != null )
                return ;
        }

        if( OnAllObjectsDestroyed != null )
            OnAllObjectsDestroyed.Invoke() ;       
    }

}

Upvotes: 2

Related Questions