public void OnBeforeSerialize()
{
// Debug.Log("before serialize ");
// create empty object only for constructor, prevent multiple calls
emptyObject = new BaseObjectData();
emptyObject.ObjectImage = gridCellEmptySprite;
Empty.Enumerate(0);
// set ids for game objects
EnumerateArray(mainObjects, 10);
EnumerateArray(overlayObjects, 100000);// EnumerateArray(underlayObjects, 200000);
EnumerateArray(boosterObjects, 300000);
}