Bridge

Decouple an abstraction from its implementation so that the two can vary independently. (Closely related to the object form of the Adaper pattern.)

Applicability

• Need to avoid a permanent binding between an abstraction (type!) and its implementation
• Both abstractions and implementation should be extensible through subclassing
• Need to isolate changes in implementations from clients
• Need to completely (.h files) hide implementation from clients
• Need to split objects because of prolifereation of classes ("nested generalizations")

Consequences

• Decouples interface and implementation
• Improves extensibility
• Hides implementation details from clients