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Statements in Class Pools and Interface Pools

Class pools and interface pools are the ABAP programs in the class library. They are defined using Class Builder tool in ABAP Workbench and are used as a repository for global classes and interfaces.

These statements are generated by Class Builder.

Each class pool or interface pool can only contain a single global class or a single global interface. These classes or interfaces are declared using the following statements:

Class Builder uses the properties entered here to generate these statements.

Other versions: 7.31 | 7.40 | 7.54

Further Statements in Class Pools

As well as the declaration of the global class, a class pool can only contain the following statements:

  • Declaration of local data types using the statement TYPES. These data types can be used by the global class in the private visibility section and in the implementation part.
  • Declaration of local constants using the statement CONSTANTS. These data types can be used by the global class in the private visibility section and in the implementation part.
  • Declaration of local interfaces using the statements INTERFACE ... ENDINTERFACE. These data types can be used by the global class in the private visibility section and in the implementation part.
  • Declaration and implementation of local classes using the statements CLASS ... ENDCLASS. These data types can be used by the global class in the private visibility section and in the implementation part.

Locally defined types, classes, and interfaces in class pools can be used in the following ways:

  • Only the methods of the global class access the local declarations and implementations in the program. These provide auxiliary methods, for example, which should not be displayed in the interface of the global class. This is the most common scenario. Any changes made to local declarations in the program do not influence the interface of the global class.
  • As well as the methods in the global class, declarations in the private visibility section of the class also reference local declarations in the program. This is a more unusual scenario, in which changes made to the local declarations influence the interface of the global class, and subclasses and friends of the global class are recompiled before the program is executed again.

Further Statements in Interface Pools

In addition to the declaration of the global interface, an interface pool cannot contain any of its own declarations or implementations.

Program Organization

Like any other ABAP program, class pools and interface pools consist of a global declaration part for declarations and an implementation part for implementations (or procedures).

  • This means that the global declaration part of a class pool can contain the declarations of local data types, local interfaces, and local classes, as well as the actual declaration part of the global class. The implementation part of a class pool can contain the implementation parts of local classes, as well as the implementation part of the global class.
  • The global declaration part of an interface pool can only contain the declaration of type groups and the declaration of the global interface. The implementation part of an interface pool is always empty.

Class Builder organizes the various declarations and implementations of a class pool or interface pool in include programs. The developer cannot usually view the names of these programs. A function in Class Builder enables the associated include programs to be opened and edited in ABAP Editor. Include programs exist for:

  • Each visibility section in the declaration part of the global class
  • Each implementation of a method of the global class
  • Local declarations and implementations
  • Test Classes for ABAP Unit

To edit the global class, Class Builder provides both editing functions for the individual include programs and a source code-based mode in which all the include programs can be displayed and edited as a single program.

Restrictions

Apart from the statements listed above, statements other than CLASS - ENDCLASS and INTERFACE - ENDINTERFACE are neither required in class pools and interface pools nor are they permitted. The stricter syntax of ABAP Objects applies to all statements permitted.

The following restrictions are particularly important:

  • No processing blocks except methods
Neither event blocks such as START-OF-SELECTION, AT SELECTION-SCREEN, GET, or AT LINE-SELECTION nor dialog modules (defined by MODULE - ENDMODULE) are permitted. This means that runtime environment events cannot be processed. ABAP Objects has its own event concept. Neither function modules nor subroutines can be defined using FUNCTION - ENDFUNCTION or FORM - ENDFORM. The methods of a class pool can still call external function modules and subroutines, as well as methods.
  • No interface work areas to other programs
The statements TABLES and NODES and the addition COMMON PART of the DATA statement are not possible. This means that class pools and interface pools do not support any global data areas across programs within a single internal session.
Screen processing as implemented in other ABAP programs is not possible. No dynpros can be defined in a class pool or interface pool. If classic dynpros, including selection screens, are required, it is best to encapsulate them in function groups. It is preferable to use other suitable output media instead of classic lists. For table list output, the classes of SAP List Viewer (ALV), such as CL_SALV_TABLE, should be used. For simple text output, we recommend browser control wrappers such as dynamic documents or text edit control wrappers.
  • No processing of extracts
Extract data sets cannot be edited in global classes since the defining statement FIELD-GROUPS is not permitted in class or interface pools.