Accessing a property of a prefab component loaded from directory during runtime

Unity Engine
1

Hi all,

I have an object in my scene that has a script attached to it that loads a prefab from my prefabs folder. This prefab has a “BillboardGroupNumber” script attached to it. I’m instantiating this prefab and attempting to update the groupNumber by doing this:

   void instantiateGroupNumberBillboard()
    {
        billboardGroupNumber = Resources.Load("Prefabs/FloatingGroupPrefab") as GameObject;
        Instantiate(billboardGroupNumber);
        Debug.Log("Created billboard with ID: " + billboardGroupNumber.GetInstanceID());
    }

    public void updateBillboardGroups()
    {
        if(billboardGroupNumber == null)
        {
            instantiateGroupNumberBillboard();
        }
      
        BillboardGroupNumber billboard = billboardGroupNumber.GetComponent(typeof(BillboardGroupNumber)) as BillboardGroupNumber;
        billboard.updateGroupNumber(5);
      
    }

The BillboardGroupNumber script looks like this:

public class BillboardGroupNumber : MonoBehaviour
{
    public int groupNumber = 0;

    void Start()
    {
        Debug.Log("Started billboard with object ID: " + this.GetInstanceID());
    }

    public void updateGroupNumber(int newGroupNumber)
    {
        groupNumber = newGroupNumber;
    }
}

I expected the groupNumber to change from the default of 0 to 5, but it still shows 0 in the inspector. I also don’t see any other instantiations. How can it not be changed? Am I somehow calling it on another object?

The 2 Instance ID’s that I’m printing do show different numbers.

2

Anybody?

3

Hi @huub8 !

Resources.Load works only for assets located in a Resources directory. If you move your Prefab to something like Prefabs/Resources/FloatingGroupPrefab.prefab your code should work as expected.

You can check the documentation for Resources.Load here Unity - Scripting API: Resources.Load

4

I wasn’t completely clear, but the Prefabs folder itself is already in the Resources folder. (and placing the prefab in the root of the Resources folder doesn’t change anything for me. Also, I do manage to create the prefab, but I just can’t seem to properly reference it.

I have made a bit of progress myself, namely that printing the object ID from the Update function within the BillboardGroupNumber gives a different ID than printing the ID of the object that I get by doing this:

BillboardGroupNumber billboard = groupNumberPrefab.GetComponent(typeof(BillboardGroupNumber)) as BillboardGroupNumber;

So the line above doesn’t work for me, the billboard reference that it produces has a positive object ID, while printing from the Update function within the actual GroupNumberBillboard gives me a different negative ID.

If I instead try to refer to the GroupNumberBillboard that has been instantiated by using Find then it does work, and I can change the value.

So this works:

BillboardGroupNumber billboard = (BillboardGroupNumber)FindObjectOfType(typeof(BillboardGroupNumber));
        billboard.updateGroupNumbers(6);

But this does not:

BillboardGroupNumber billboard = groupNumberPrefab.GetComponent(typeof(BillboardGroupNumber)) as BillboardGroupNumber;
        billboard.updateGroupNumbers(5);

Using find is not ideal, since I will be having multiple BillboardGroupNumber objects, and I still don’t understand what I’m doing wrong in the first place.

5

Your problem is that you are querying the component from the asset object and not the created clone. So something like this should fix your problem:

var floatingGroupPrefabAsset = Resources.Load("Prefabs/FloatingGroupPrefab") as GameObject;
var floatingGroup = Instantiate(floatingGroupPrefabAsset);
var billboardGroupNumber = floatingGroup.GetComponent<BillboardGroupNumber>();
billboardGroupNumber.updateGroupNumbers(6);
6

Ah yes! That is exactly what I was doing wrong. Thank you!