Mediator

Static diagram :

Description :

Type :

Be  (Behavioral)

Intent :

Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.

Applicability :

Use the Mediator pattern when : - a set of objects communicate in well-defined but complex ways. The resulting interdependencies are unstructured and difficult to understand. - reusing an object is difficult because it refers to and communicates with many other objects. - a behavior that's distributed between several classes should be customizable without a lot of subclassing.

Pattern's participants :

• Mediator
  Defines an interface for communicating with Colleague objects.
• ConcreteMediator
  Implements cooperative behavior by coordinating Colleague objects.
  Knows and maintains its colleagues.
• Colleague classes
  Each Colleague class knows its Mediator object.
  Each colleague communicates with its mediator whenever it would have otherwise communicated with another colleague.

Spoiled patterns :

1. 1. Complete collaboration between concrete colleagues

Problems :

1. 1. The control tower