Observer Pattern

• Subject
• The class whose instances independently change their state and notify Observers
• IObserver
• An interface for Observers specifying how they should be updated
• Observer
• A class that provides an Update method to enable its instance’s state to stay consistent with the Subject’s
• Update
• The operation that forms the interface between the Subject and the Observers
• Notify
• The event mechanism for calling the Update operation on all Observers