how to access GameObject by instance id in Unity

Question

In Unity, it provides a function to get the instance of GameObject

GetInstanceID ()

While the instance id could differ GameObjects, but the function to get GameObject by instance id

InstanceIDToObject()

is only provided in EditorUtility, which can't use in release.

As far as I think, using HashTable maybe is a method to reach that, but is t here any other method to achieve that?

The only way that might be possible is through reflection but that's not worth it due to performance reasons. Stick to HashTable or Dictionary. — Programmer
– Programmer, Commented May 17, 2017 at 6:33

matiaslauriti · Accepted Answer · 2017-05-18 00:21:33Z

9

Solution can be found on Unity forums, I'll quote for convenience.

Not directly, but you can use the InstanceID to rename the object, and then do a GameObject.Find using the InstanceID to access the object that way.

gameObject.name = GetInstanceID().ToString();
var foo = 38375; // A made-up InstanceId...in actual code you'd get this from a real object...you can store the instance ids in an array or something
GameObject.Find(foo.ToString()).transform.position = whatever;

I've also had a hashtable and used the instance ids as keys for the hashtable in order to access each object. You can go through and assign objects an identifier yourself, but since every object has a unique InstanceID() anyway, might as well use it if the situation calls for it.

Source: https://forum.unity3d.com/threads/can-i-use-instanceid-to-access-an-object.12817/

edited May 18, 2017 at 0:21

matiaslauriti

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answered May 17, 2017 at 6:35

Bazgrim

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2 Comments

Farhan Over a year ago

This should be accepted as answer. However, you should never have to Find an object, it a bad performance hit if you have too many of finds in your code. If you must, consider FindWithTag, it is faster, provided you don't put the same tag on too many objects. Generally, keep references of what you could have to find.

John Stock Over a year ago

No it should not be accepted as the answer as it doesn't answer the question, it's a workaround that requires you to rename objects. A proper answer would not require that.

Stephen Rauch · Accepted Answer · 2018-05-27 14:36:45Z

1

public static GameObject getObjectById(int id)
{
    Dictionary<int, GameObject> m_instanceMap = new Dictionary<int, GameObject>();
    //record instance map

    m_instanceMap.Clear();
    List<GameObject> gos = new List<GameObject>();
    foreach (GameObject go in Resources.FindObjectsOfTypeAll(typeof(GameObject)))
    {
        if (gos.Contains(go))
        {
            continue;
        }
        gos.Add(go);
        m_instanceMap[go.GetInstanceID()] = go;
    }

    if (m_instanceMap.ContainsKey(id))
    {
        return m_instanceMap[id];
    }
    else
    {
        return null;
    }
}

edited May 27, 2018 at 14:36

Stephen Rauch♦

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answered May 27, 2018 at 14:07

Taivas Gogoljuk

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