Inheritance and Interfaces

Interfaces are independent constructs in ABAP Objects that support polymorphism of classses. The polymorphism of interfaces is based on the fact that each class implementing an interface can implement the methods of that interface differently. To the outside world, all interface components look similar which is why interface reference variables can point to objects of all classes that implement the associated interface. The interface concept exists independently of and in addition to the inheritance concept.The classes of an inheritance tree can implement any number of interfaces but each interface can be implemented only once in each inheritance tree. This ensures that each interface component comp has a unique name in the entire inheritance tree intf~icomp and that, starting with the class that implements it, it is contained in all subclasses.

Interface reference variables that can point to a class of the inheritance tree can also point to all subclasses. Having been implemented, interface methods are fully functioning components of a class and can be redefined in subclasses.