a set of objects communicate in well-defined but complex ways.

communicates with the Mediator whenever it would have otherwise communicated with another Colleague.ДЄpplicability According to Gamma et al, the Mediator pattern should be used when:

Colleague classes - keep a reference to its Mediator object.

implements the communication and transfer the messages between the colleague classes

ConcreteMediator - knows the colleague classes and keep a reference to the colleague objects.

Mediator - defines an interface for communicating with Colleague objects.

Participants The participants classes in this pattern are: Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently. IntentДefine an object that encapsulates how a set of objects interact. All the operations between controls are managed by the form class itself.

As you have seen if you created different applications using forms you don't have to modify each control class each time you add a new control to the form.

For example when a button is pressed it must know if the data is valid in other controls. This control need to interact with all the other control. When we create it we add all sort of controls to the screen. In order to avoid tight coupled frameworks, we need a mechanism to facilitate the interaction between objects in a manner in that objects are not aware of the existence of other objects. If certain principles are not applied the final framework will end in a total mess where each object relies on many other objects in order to run. In order to have a good object oriented design we have to create lots of classes interacting one with each other.

Mediator 9 templates