Changed values do not persist

I have a process that I need to run, in the editor, to automatically generate/fill in data on certain objects.

Creating a new Tool Menu in the Editor allows me to do this, however my changes are only temporary. If the object I am changing is an instance of a prefab, it will revert back to the empty prefab values (even though changing those values does not break the prefab).

I need these changes to stick when using a pre-fab. Is there some way to do this?

I am creating the menu entry with the following code.

Code (CSharp):

1. public class NewBehaviourScript
2. {
3.     [MenuItem("Tools/Do Something")]
4.     private static void NewMenuOption()
5.     {                
6.         GameObject[] things = GameObject.FindGameObjectsWithTag("thing");
7.         foreach (GameObject thing in things)
8.         {
9.             thing.GetComponent<SomeThing>().someValue = 10;
10.             EditorUtility.SetDirty(thing);
11.         }
12.  
13.         EditorSceneManager.MarkSceneDirty(SceneManager.GetActiveScene());
14.     }
15. }

 

You can do this with PrefabUtility: https://docs.unity3d.com/ScriptRefe...ecordPrefabInstancePropertyModifications.html