Mediator Design Pattern

The Mediator Design Pattern is a behavioral design pattern that defines an object (the mediator) to centralize communication and coordination between multiple objects (colleague components) in a system. Instead of these objects directly interacting with each other, they communicate through the mediator, promoting loose coupling and making the system more maintainable and extensible.

Key points of the Mediator Design Pattern:

1. Intent:

   • The main intent of the Mediator pattern is to define an object that centralizes communication and coordination between a set of objects. It helps in reducing direct dependencies between the objects by allowing them to communicate indirectly through the mediator.

2. Key Components:

   • Mediator:
     • Defines an interface for communicating with Colleague objects. It encapsulates the communication logic and coordinates interactions between the colleagues.
   • ConcreteMediator:
     • Implements the Mediator interface and coordinates the communication between the colleagues. It is aware of each colleague and their interactions.
   • Colleague:
     • Defines an interface for communicating with other colleagues through the mediator. Colleagues are not aware of each other and communicate only through the mediator.
   • ConcreteColleague:
     • Implements the Colleague interface. It is a participant in the communication and interacts with other colleagues through the mediator.

3. Centralized Communication:

   • The Mediator pattern centralizes communication logic, preventing direct communication between colleagues. Colleagues interact with each other only through the mediator.

4. Reduced Dependencies:

   • Colleagues are decoupled from each other, reducing dependencies and making the system more maintainable and extensible. Adding new colleagues or changing the interaction logic is easier.

5. Promotes Flexibility:

   • Because communication is centralized in the mediator, it's easier to change or extend the interaction behavior without modifying individual colleagues.

6. Advantages:

   • Decoupling: It reduces the direct dependencies between objects, promoting a more flexible and maintainable design.
   • Reusability: Colleagues can be reused in different contexts since their interactions are managed by the mediator.

7. Use Cases:

   • The Mediator pattern is suitable when a set of objects need to communicate with each other, but direct dependencies between them should be minimized.
   • It is useful when adding new objects or changing the communication logic between objects is a common requirement.

8. Example:

   • Consider a graphical user interface framework where different GUI components (colleagues) such as buttons, text fields, and checkboxes need to interact. The Mediator pattern could be used to centralize the communication and coordination between these components.