Redefining Methods

Each subclass contains the components of all classes that lie between this class and the root node in the inheritance tree. The visibility of a component is always the same and cannot be changed. However, it is possible to redefine the public and protected instance methods of all preceding superclasses using the REDEFINITION addition of the METHODS statement in order to adjust them to the requested specialization. The interface of a redefined method cannot be changed. The method is merely re-implemented under the same name. Constructors cannot be redefined; instead, special rules apply.

The method declaration remains with the superclass, and its previous implementation is also retained there. The implementation of the redefinition is generated additionally with the subclass and obscures the implementation of the superclass. A redefined method works with the private attributes of the subclass and not with possible private superclass attributes of the same name.

Each reference that points to a subclass object uses the redefined method, even if it was typed with reference to a superclass. In particular, this also applies to the self-reference me. For example, if a superclass method m1 contains a call [me->]m2( ) or CALL METHOD [me->]m2 and if m2 is redefined in a subclass, the call of m1 in an instance of the superclass causes the original method m2 to be executed and the call of m1 in an instance of the subclass causes the redefined method m2 to be executed.

Within a redefined method the pseudo reference super-> can be used to access the obscured method, for example, to adopt and supplement its functions.