Mediator

Several objects have to be changed simultaneously however they do not form a hiararchy as in the Chain of Responsibility. If they communicate with each other, they have to keep a record of each other. A convenient way is to introduce a Mediator to loosen up their coupling.

However, now the ConcreteMediator must keep a record of all Collegues. Each ConcreteCollegue inform the Mediator by passing its pointer. The advantages of a Meditator are

• It limits subclassing of Collegues.
• It centralizes controls.
• The communication of Collegues become easier.

In reality the interface of Meditator is not indispensable.