Custom Editor: Field reverts after saving and closing/reloading scene

I have an editor script that calls an external method in OnInspectorGUI() to set a serialized field.

I use 'Undo.RecordObject' in the external method. But when I save, close and reload the scene, the field hasn't saved the changes (the field is a GameObject reference). What do I need to do get this to save properly?

Code (CSharp):

1. public override void OnInspectorGUI()
2. {
3.    serializedObject.Update();
4.  
5.    UniqueObjectId uniqueObjectId = target as UniqueObjectId;
6.  
7.    EditorGUILayout.PropertyField(idString);
8.    EditorGUILayout.PropertyField(objectListManager);
9.  
10.    GUILayout.BeginHorizontal();
11.    if (GUILayout.Button("Get ObjectListManager"))
12.    {
13.        uniqueObjectId.GetObjectListManager();
14.    }
15.    if (GUILayout.Button("Generate ID String"))
16.    {
17.        uniqueObjectId.GenerateIfEmpty();
18.    }
19.     GUILayout.EndHorizontal();
20.  
21.    serializedObject.ApplyModifiedProperties();
22. }

Code (CSharp):

1. public virtual void GetObjectListManager()
2. {
3.     var managers = GameObject.FindGameObjectWithTag("Managers");
4.     if (managers)
5.     {
6.         if (objectListType == ObjectListType.Scene)
7.         {
8. #if UNITY_EDITOR
9.             Undo.RecordObject(this, "Set Object List Manager");
10. #endif
11.             objectListManager = managers.GetComponentInChildren<SceneObjectListManager>();
12.         }
13.         else if (objectListType == ObjectListType.Dynamic)
14.         {
15. #if UNITY_EDITOR
16.             Undo.RecordObject(this, "Set Object List Manager");
17. #endif
18.             objectListManager = managers.GetComponentInChildren<DynamicObjectListManager>();
19.         }
20.     }
21. }

 

This might be the solution, I'm not sure.

Code (CSharp):

1.  
2. public override void OnInspectorGUI(){
3.    EditorGUI.BeginChangeCheck();
4.    //your functions
5.    if(EditorGUI.EndChangeCheck()){
6.         EditorUtility.SetDirty(this);
7.    }
8. }

 

I changed 'GetObjectListManager' to a function and changed the button code to set the 'objectReferenceValue' of the field to take its return value and it seems to work now.

Code (CSharp):

1. if (GUILayout.Button("Get ObjectListManager"))
2. {
3.     objectListManager.objectReferenceValue = uniqueObjectId.GetObjectListManager();
4. }