Coroutines not running code after yield return – Unity C# script

I am trying to detonate a grenade (which is working) and then after a delay, remove the objects that are damaged from the scene, to clear up what the player is looking at. Because the delay needs to begin only once the grenade has exploded, I can’t use a timer set-up in the Update() function, as other solutions on here have suggested (like you can see I’m doing for the detonation countdown).

Invoke() also won’t work because I need to pass in the nearby object colliders as a parameter. I’ve been hunting a solution for a day now, but I just can’t make it work.

My code is here:

public class Grenade : MonoBehaviour
{

public float delay = 3f;
private float countdown;
private bool hasExploded = false;
public GameObject explosionEffect;
public float explosionForce;
public float damageRadius;
public float destroyDelayTime = 3.0f;

void Start()
{
    countdown = delay;
}

void Update()
{
    // start countdown
    countdown -= Time.deltaTime;

    // run explode method
    if (countdown <= 0 && !hasExploded)
    {
        Explode();
        hasExploded = true;
    }
}

private void Explode()
{
    // Show explosion effect (cut out to simplify my question, but works fine)
    // Get nearby objects
    Collider[] colliders = Physics.OverlapSphere(transform.position, damageRadius);
    // Apply explosion force to each object (again cut out, but works fine)

    // destroy grenade object
    Destroy(gameObject);
    Debug.Log("Grenade destroyed");

    // destroy nearby objects after a delay
    StartCoroutine(DelayObjectDestroy(colliders, destroyDelayTime));
}

IEnumerator DelayObjectDestroy(Collider[] colliders, float delay)
{
    Debug.Log("DelayObjectDestroy called");
    yield return new WaitForSeconds(3.0f); // will replace 3.0f with 'delay' once it is working
    Debug.Log("Objects destroyed");
}
}

The Debug.Log("DelayObjectDestroy called"); line gets displayed in the console so I know the coroutine is indeed being called. The Debug.Log("Objects destroyed"); line doesn’t show in the console though, even after waiting a very long time.

There is no superclass other than MonoBehaviour, and no errors appear in the console.

What confuses me even more is that I made a fresh, plain script and attached it to the camera just to see if a coroutine would work, and it worked exactly as it should. Why does this code work but my grenade script doesn’t?

public class camera : MonoBehaviour
{
    void Start()
    {
        StartCoroutine(meh());
    }

    private IEnumerator meh()
    {
        Debug.Log("Game started");
        yield return new WaitForSeconds(8.0f);
        Debug.Log("Game ended");
    }
}

At start, "Game started" is displayed in the console. After an 8 second delay, "Game ended" is displayed in the console.

>Solution :

Because you call

 Destroy(gameObject);

so your object which is running this coroutine doesn’t exist anymore => The routine executes everything to the first yield instruction.

After that it basically doesn’t exist anymore for the engine.

You either need to wait with destroying the grenade … or in your case I would simply introduce an always existing routine executer like e.g.

public class CoroutineRunner : MonoBehaviour
{
    public static CoroutineRunner Instance { get; private set; }

    private void Awake()
    {
        if(Instance && Instance != this)
        {
            Destroy(gameObject);
            return;
        }

        Instance = this;
    }
}

and then do

CoroutineRunner.Instance.StartCoroutine(DelayObjectDestroy(colliders, destroyDelayTime));

Note though: You still may not access any of the built-in properties and methods anymore which would require the grenade GameObject to still exist!