In Swift, the Mediator Design Pattern can be implemented by defining a protocol that declares the methods and properties that the mediator should have. This protocol can then be adopted by a class that acts as the mediator, coordinating communication between the different objects that use it.
To illustrate how this pattern can be used in Swift, let's consider a simple example of a chat application. In this application, we have several chat rooms, each of which has multiple users. We want to design the communication between the chat rooms and the users in such a way that the chat rooms and users are not directly dependent on each other.
To achieve this, we can define a ChatRoomMediator protocol that declares the methods and properties that the mediator should have. This protocol can be adopted by a ChatRoom class, which will act as the mediator for the different chat rooms in the application.