Klassenswitch

Klassenswitch is a concept in object-oriented programming that describes the ability to change an object's class at runtime in order to alter its behavior. The term, a German construction meaning “class switch,” appears in discussions of dynamic languages and metaprogramming where the type or role of an object can be modified without creating a new instance.

In practice, Klassenswitch is not a standard feature of most statically typed languages. In languages with dynamic type systems, it can be achieved by modifying the object's class reference, extending or replacing its behavior through mixins or modules, or swapping the method dispatch mechanism. Common approaches to implement a form of Klassenswitch include the State pattern, the Strategy pattern, or dynamic composition via delegation, where an object changes behavior by routing operations to different components rather than by a fixed class change.

Use cases include runtime feature toggles, A/B testing of object behavior, or modelling entities that assume different roles or states during their lifecycle, such as a game character that shifts between “ally” and “enemy” roles or a service object that adopts different strategies based on configuration.

Limitations and considerations are significant. Changing an object’s class or behavior at runtime can introduce complexity, make invariants harder to maintain, and risk type-safety or encapsulation guarantees. As a result, many language communities prefer clearer patterns such as explicit state machines, composition over inheritance, or well-defined metaprogramming facilities to achieve similar flexibility.

See also: dynamic dispatch, metaprogramming, State pattern, Strategy pattern, mixins, object composition.