Intent
Decouple an abstraction from its implementation so that the two can vary independently. Also known as Handle/Body.
Where to use & benefits
- Want to separate abstraction and implementation permanently
- Share an implementation among multiple objects
- Want to improve extensibility
- Hide implementation details from clients
Structure
Participants
Abstraction (MainApplet)
It defines the abstraction's interface and maintains a reference to an object of type Implementor.
RefinedAbstraction
Extends the interface defined by Abstraction.
Implementor (IAppletGUIBuilder)
defines the interface for implementation classes. This interface can be quite different to Abstraction's interface.
ConcreteImplementor (ButtonBuilder, ListBuilder)
implements the Implementor interface and defines its concrete implementation.
Example
In the demonstration application, the bridge pattern is not implemented as a whole, but the MainApplet class act as the Abstraction to maintain the reference of different objects of its type implementor.