Modify prefabs in editor script

Questions & Answers
1

I am trying to write a script that will update the material settings on a set of prefabs, which I can then save.

I have seen a number of questions asking to do this, but none of the examples work. My code is below.

Whenever I run this, the editor reacts by re-importing assets, and there are no exceptions indicating that my call to ReplacePrefab() is incorrect - but the prefabs themselves remains unchanged.

What have I missed?

    AssetDatabase.StartAssetEditing();

	var guids = AssetDatabase.FindAssets(" t:GameObject",new string[]{"Assets/city_assets"});
	foreach(var g in guids)
	{
		string path = AssetDatabase.GUIDToAssetPath(g);
		GameObject prefab = AssetDatabase.LoadAssetAtPath(path, typeof(GameObject)) as GameObject;

		GameObject instance = Object.Instantiate(prefab);

		UpdateMaterials(instance); //operates on the components of instance

		PrefabUtility.ReplacePrefab(instance, prefab, ReplacePrefabOptions.ConnectToPrefab);
	}

   AssetDatabase.StopAssetEditing();
2

try PrefabUtility.InstantiatePrefab instead of Object.Instantiate, and call AssetDatabase.SaveAssets() after you finish all the work