Callback for object between NSViewController

Hi, This question is similar to a previous post (Return values for NSViewController) but the difference now is that the return from VC2 to VC1 is an object. Problem description: The NSViewController VC1 activates the NSViewController VC2 using the segue and passes by delegate an OBJ object of a class instantiated in VC1. VC2 changes the values of OBJ properties, and calls dismiss to return focus to VC1. How to make VC1 be notified immediately when VC2 closes? Obs. I created a method in VC1 triggered by a button that confirms that the values of the OBJ properties were really changed.