(Solved): I currently have a UML Diagram for a Library Management System. I have added an interface IEvent and ...

I currently have a UML Diagram for a Library Management System. I have added an interface IEvent and I am trying to add an event bus to it but I do not understand if I am on the right track.  

This is my current UML Diagram without the event bus: 

 This is a starting idea I have for the event bus. I want to create one so that when an item is loaned, the reservation screen knows what to do:

I am unsure on whether the publisher needs a post() method as well, or whether the subscriber needs their own methods such as update() and display().