ABAP Keyword Documentation → ABAP - Reference → Declarations → Declaration Statements → Classes and Interfaces → Components in Classes and Interfaces → Implementing and including interfaces → INTERFACES
Within the declaration of an interface, the
INTERFACES statement integrates
intf in the declared interface. You cannot specify an additions. As a result, the interface
intf becomes a component interface of a composite interface.
An interface can be composed of any number of different component interfaces. All these interfaces are equally valid on one level. If a component interface itself is a composite (that is, it contains its own component interfaces) the nesting hierarchy is irrelevant for the composition of the interface. It is relevant, however, for accessing the interface components.
To access a component
comp of a component interface
within a composite interface, you can use the expression
intf~comp with the
interface component selector
(~). Multiple use of the interace component
selection in an identifier (such as
intf1~intf2~comp) is generally not supported.
Within a composite interface, you can use the interface component selector to access only interface
components of the component interface that are integrated in this interface using the statement
INTERFACES. Since all nested interfaces are at the same level, however, all that is needed to access the interface components of all component interfaces is the name of their interface.
- Each interface and its components appear only once in a composite interface. Even an interface that is seemingly implemented more than once in an interface, because it is an interface component of one or more other interfaces, really exists only once.
Since there are no separate namespaces for global and local interfaces, you have to make sure that compositions
of local interfaces do not result in combinations of global and local interfaces with identical names, because they cannot be equally valid on the same level in their implementation.
The following example illustrates how you can use the
to compose and implement interfaces. Class
c1 implements the composite interfaces
is a component interface of
i3, it exists
only once in class
c1. A reference variables
of the static type
i1 is used to generate an object class
c1 and call method
i1~m1, which is implemented there.
INTERFACE i1. METHODS m1. ENDINTERFACE. INTERFACE i2. INTERFACES i1. METHODS m2. ENDINTERFACE. INTERFACE i3. INTERFACES i1. METHODS m3. ENDINTERFACE. CLASS c1 DEFINITION. PUBLIC SECTION. INTERFACES: i2, i3. ENDCLASS. CLASS c1 IMPLEMENTATION. METHOD i1~m1. ... ENDMETHOD. METHOD i2~m2. ... ENDMETHOD. METHOD i3~m3. ... ENDMETHOD. ENDCLASS. DATA iref1 TYPE REF TO i1. START-OF-SELECTION. CREATE OBJECT iref1 TYPE c1. iref1->m1( ).