FlexibleService

Behavioral

Intent

Decouple a behavior from an ancestor class so that the descendant classes dynamically specify a specific behavior.

Solution

• Use the Objectifier pattern to provide a class hierarchy of easily variable services packaged in object classes.
• Apply the Template Method pattern to define methods in the AbstractClient which request a ConcreteSubject reference by calling GetService().
• Override GetService() in ConcreteClient and return ConcreteService.

Consequences

• Results in extremely flexible and extensible framework designs.
• ConcreteClients  completely control the specific service used and may change service objects on the fly as needed.
• Adds additional overhead since each service call is preceded by a call-back to GetService().

Related Patterns

• Flexible Service combines Objectifier with Template Method
• Flexible Service is similar to Bridge

Source: [oodwksp]

OO Workshop

The NASA / Korson-McGregor Object-Oriented Design Workshop, David Van Camp, Goddard Spaceflight Center (offsite), NASA, Lanham, MD, 1997—1998.