Mediator Pattern - Decoupling the interactions between objects

The Mediator pattern is a behavioral design pattern that promotes loose coupling between objects by encapsulating and controlling the communication and coordination between them. It encourages objects to communicate with each other through a mediator object rather than directly.

In a software system, when multiple objects need to interact with each other, the direct communication between them can result in increased complexity and dependencies. This makes the system difficult to maintain and modify. The Mediator pattern solves this problem by introducing a mediator object that handles the communication between the objects, ensuring that they are decoupled from each other.

How does it work?

The Mediator pattern consists of the following components:

  1. Mediator: This is an interface or abstract class that defines the communication interface between objects. It declares methods that objects can use to communicate with each other.

  2. Concrete Mediator: This is a concrete implementation of the Mediator interface. It manages the communication and coordinates the interactions between objects.

  3. Colleague: This represents the objects that need to communicate with each other. They are aware of the mediator and use it to send and receive messages.

The mediator acts as an intermediary between the colleagues, allowing them to communicate without knowing each other's details. Each colleague object only needs to know about the mediator and not about the other colleagues. This decouples the objects and reduces the dependencies, making the system more flexible and maintainable.

Benefits of using the Mediator Pattern

The Mediator pattern provides several benefits:

  1. Decoupling: The pattern decouples the interactions between objects by removing direct references between them. This reduces dependencies and makes the code more modular and flexible.

  2. Simplified communication: By centralizing the communication logic in the mediator, the pattern simplifies the communication process between objects. It eliminates the need for complex communication logic in each individual object.

  3. Improved maintainability: With decoupled objects, it becomes easier to modify or extend the system. Changes made to one object do not affect the others, making the code easier to maintain.

  4. Reusability: The mediator object can be reused across different sets of colleagues, promoting code reusability.

Example usage

Let's consider an example of a chat application. The chat application consists of multiple users who can send messages to each other. Without using the Mediator pattern, each user would need to have direct references to other users for communication. This would lead to high coupling and increased complexity.

Using the Mediator pattern, we can introduce a ChatMediator that handles the communication between users. Each user is a Colleague, and they communicate through the ChatMediator. When a user sends a message, it is sent to the ChatMediator, which then forwards it to the intended recipient(s). This way, the users are decoupled from each other, and the communication logic is centralized in the ChatMediator.


The Mediator pattern is an effective way to decouple the interactions between objects in a software system. By introducing a mediator object, it simplifies and centralizes the communication process, making the code more maintainable and flexible. It promotes loose coupling between objects and reduces dependencies, leading to more modular and reusable code. Consider using the Mediator pattern when you have a system with complex interactions between objects that need to be decoupled.

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