CSC/ECE 517 Fall 2012/ch2b 2w43 iv

Mediator Pattern

Introduction

Mediator pattern comes under the category of behavioral pattern. It specifies an object that includes the encapsulation about the interaction among various objects.

It prevents objects to interact with each other explicitly and thus it facilitates loose coupling. In other words it handles complex communication among related objects. All the objects communicate with the mediator when they want to interact with each other. Thus it improves maintainability.

All the classes which interact with the mediator are called colleagues. These colleagues know who their mediator is and the mediator also knows which colleagues can interact with it. The colleagues send messages to the mediator object. The mediator sends message to other classes. Thus the object which initiated this communication does not need to have knowledge about other objects. All they need to know is about their mediator who is responsible to carry out this communication.

Following classes/objects take part in this process:

Mediator: Provides interface for communication among colleagues.

Concrete Mediator: It coordinates the colleagues and implements cooperative behavior. It also holds information about the colleagues.

Colleague Classes: Colleague classes know about their mediator.

A real life example of mediator pattern can be of an airport control tower. It is the job of this tower to control all the planes. It decides which plane will take-off and land at what time rather than plane to plane communication.

Another example of mediator pattern

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