Key Relationships

• Mediator - Observer
  • Mediator provides a way to keep interacting objects loosely coupled
    by defining a Mediator object that centralizes (encapsulates) interaction behavior.
  • Observer provides a way to keep interacting objects loosely coupled
    by defining Subject and Observer objects that distribute interaction behavior so that when a subject changes state all registered observers are updated.
  • "The difference between them is that Observer distributes communication by introducing Observer and Subject objects, whereas a Mediator object encapsulates the communication between other objects." [GoF, p346]