# \[Beginner\] How do I check, if an event instance is assigned a specific event reference?

**URL:** <https://qa.fmod.com/t/beginner-how-do-i-check-if-an-event-instance-is-assigned-a-specific-event-reference/20270>\
**Category:** Unity\
**Tags:** unity\
**Created:** [June 1, 2023, 1:03pm UTC](https://qa.fmod.com/t/beginner-how-do-i-check-if-an-event-instance-is-assigned-a-specific-event-reference/20270 "2023-06-01T13:03:38Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Alemay36](https://avatars.discourse-cdn.com/v4/letter/a/e9bcb4/32.png) [@Alemay36](https://qa.fmod.com/u/Alemay36)\
**Post date:** [June 1, 2023, 1:03pm UTC](https://qa.fmod.com/t/beginner-how-do-i-check-if-an-event-instance-is-assigned-a-specific-event-reference/20270/1 "2023-06-01T13:03:38Z")

</div>

Hello everyone!

I started learning Unity and FMOD for a work project a few weeks ago and have now gotten to a problem, that a tutorial or Google search couldn’t solve:

In my code, I want to check, if my EventInstance called “Audio” is set to a specific value / assigned to a specific Event.

Essentially I want to play a certain sound event for different distances between the sound source and the player (in 3D). So my plan was to create an EventInstance in the Start() function as a default event that plays when the game starts. Then it checks in the FixedUpdate() function, if the player is in a certain distance (%) on the way to the object.  
If that is the case it’s supposed to check if the corresponding event is **not** playing and if that’s the case, it should destroy the previous EventInstance and create a new one under the same name (Audio), playing the correct event instead.  
I tried the standard C#: if (Audio != “EventReferenceName”) which doesn’t seem to work.

Here is my code:  
(ignore the occlusion and linecasting stuff, I took a script from Scott Game Sounds as a basis and that part works without any issues)

```auto
using UnityEngine;
using FMODUnity;
using FMOD.Studio;

public class FirstPersonOcclusion : MonoBehaviour
{
    [Header("FMOD Event")]
    [SerializeField]
    private EventReference Ueber75;
    [SerializeField]
    private EventReference Audio75;
    [SerializeField]
    private EventReference Audio50;
    [SerializeField]
    private EventReference Audio25;
    [SerializeField]
    private EventReference Audio5;
    private EventInstance Audio;
    private EventDescription AudioDes;
    private StudioListener Listener;
    private PLAYBACK_STATE pb;

    [Header("Occlusion Options")]
    [SerializeField]
    [Range(0f, 10f)]
    private float SoundOcclusionWidening = 1f;
    [SerializeField]
    [Range(0f, 10f)]
    private float PlayerOcclusionWidening = 1f;
    [SerializeField]
    private LayerMask OcclusionLayer;

    private bool AudioIsVirtual;
    private float MaxDistance;
    private float ListenerDistance;
    private float StartDistance;
    private float lineCastHitCount = 0f;
    private Color colour;

    private void Start()
    {
        Audio = RuntimeManager.CreateInstance(Ueber75);
        RuntimeManager.AttachInstanceToGameObject(Audio, GetComponent<Transform>(), GetComponent<Rigidbody>());
        Audio.start();
        Audio.release();

        AudioDes = RuntimeManager.GetEventDescription(Ueber75);
        AudioDes.getMinMaxDistance(out float MinDistance, out MaxDistance);

        Listener = FindObjectOfType<StudioListener>();

        Vector3 StartingPosition = new Vector3(Listener.transform.position.x, Listener.transform.position.y, Listener.transform.position.z);
        StartDistance = Vector3.Distance(StartingPosition, transform.position);
    }

    private void FixedUpdate()
    {
        Audio.isVirtual(out AudioIsVirtual);
        Audio.getPlaybackState(out pb);
        ListenerDistance = Vector3.Distance(transform.position, Listener.transform.position);

        if (!AudioIsVirtual && pb == PLAYBACK_STATE.PLAYING)
            OccludeBetween(transform.position, Listener.transform.position);

        lineCastHitCount = 0f;

        if (ListenerDistance <= (StartDistance / 100 * 75) && ListenerDistance > (StartDistance / 100 * 50))
        {
            if (//Check here if EventInstance "Audio" has NOT the value "Audio75")
            {
                Audio.stop(FMOD.Studio.STOP_MODE.IMMEDIATE);
                Audio = RuntimeManager.CreateInstance(Audio75);
                RuntimeManager.AttachInstanceToGameObject(Audio, GetComponent<Transform>(), GetComponent<Rigidbody>());
                Audio.start();
                Audio.release();

                AudioDes = RuntimeManager.GetEventDescription(Audio75);
            }
        }

```

Maybe you can also tell me if something else should be changed. For example I also am not sure if the previous EventInstance actually gets properly destroyed here; or maybe I have to make a new variable for every specific distance too(?).

Anyways, thanks for your patience!

---

<div class="post-metadata">

**Author:** ![Alemay36](https://avatars.discourse-cdn.com/v4/letter/a/e9bcb4/32.png) [@Alemay36](https://qa.fmod.com/u/Alemay36)\
**Post date:** [June 2, 2023, 11:03am UTC](https://qa.fmod.com/t/beginner-how-do-i-check-if-an-event-instance-is-assigned-a-specific-event-reference/20270/2 "2023-06-02T11:03:32Z")

</div>

After asking ChatGPT for an hour, I finally got a working solution for my problem. I still don’t 100% know why exactly it works or what it does, but I will try to find that out. The working code is:

```auto
if (ListenerDistance <= (StartDistance / 100 * 75) && ListenerDistance > (StartDistance / 100 * 50))
        {
            EventDescription audio75Des = RuntimeManager.GetEventDescription(Audio75);

            if (AudioDes.isValid() && AudioDes.handle != audio75Des.handle)
            {
                Audio.stop(FMOD.Studio.STOP_MODE.ALLOWFADEOUT);
                Audio = RuntimeManager.CreateInstance(Audio75);
                RuntimeManager.AttachInstanceToGameObject(Audio, GetComponent<Transform>(), GetComponent<Rigidbody>());
                Audio.start();
                Audio.release();

                AudioDes = RuntimeManager.GetEventDescription(Audio75);
            }

```

The thing that makes me question is the lower case “a” in “audio75Des.handle”, because usually all the variables in the code start with a capital A. Is this a new variable? The “EventDescription” and .handle stuff is still a little confusing for me.

---

<div class="post-metadata">

**Author:** ![Connor\_FMOD](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/connor_fmod/32/3685_2.png) [@Connor\_FMOD](https://qa.fmod.com/u/Connor_FMOD)\
**Post date:** [June 6, 2023, 12:39am UTC](https://qa.fmod.com/t/beginner-how-do-i-check-if-an-event-instance-is-assigned-a-specific-event-reference/20270/3 "2023-06-06T00:39:34Z")

</div>

Hi,

There are a couple of options for checking event description identities. either `EventDescription::getID()` or `EventDesctription::getPath()` ([FMOD API | Studio API Reference - Studio::EventDescription](https://fmod.com/docs/2.02/api/studio-api-eventdescription.html#:~:text=User%20property%20types.-,General%3A,-Studio%3A%3AEventDescription%3A%3AgetID)) but checking the `.handle` is valid too.

> [@Alemay36](#):
>
> I also am not sure if the previous EventInstance actually gets properly destroyed here

Yes, as you are calling `release()` on the event before you are reassigning it means it should be cleaned up by the FMOD system after you call `Audio.stop(FMOD.Studio.STOP_MODE.ALLOWFADEOUT);`. I would suggest maybe checking `!Audio.isValid()` before assigning it to the new event just to be safe.

I will also link to our Unity Scripting Examples which have lots of examples using our API with Unity which might be a useful reference: [Unity Integration | Scripting Examples](https://fmod.com/docs/2.02/unity/examples.html).

If you have any more questions please do not hesitate to ask!