SAP NetWeaver AS ABAP Release 740, ©Copyright 2014 SAP AG. All rights reserved.
ABAP Keyword Documentation →
ABAP − Reference →
Program structure →
Modularization Statements →
Procedures →
Function Modules →
FUNCTION →
Function Module Interface
The parameter interface
of a function module is defined in Function Builder. It includes the definition of interface parameters
and the specification of exceptions that can be raised by a function module. Function Builder automatically
generates comment lines below the FUNCTION
statement in the source code of the function module. These represent the interface of the function module with the following syntax:
Syntax
... [IMPORTING parameters]
[EXPORTING parameters]
[TABLES table_parameters]
[CHANGING parameters]
[{RAISING exc1|RESUMABLE(exc1) exc2|RESUMABLE(exc2) ...}
|{EXCEPTIONS exc1 exc2 ...}]
The syntax and semantics of IMPORTING, EXPORTING,
CHANGING, RAISING, and EXCEPTIONS
mainly correspond to the definition of method interfaces with
[CLASS-]METHODS. The additional option of defining table parameters using TABLES is obsolete.
Note
The ABAP Development Tools do not
have a form-based Function Builder and the parameter interface of a function module is defined in an
ABAP pseudo syntax. These statements are not compiled like genuine ABAP statements and the regular ABAP
syntax checks are not applied. When a function module is generated, they are interpreted like the form-based instructions from the classical Function Builder.
Interface Parameters
The interface parameters are defined on the relevant tab pages in Function Builder.
- IMPORTING parameters are input parameters. When the function module is
called, a suitable actual parameter must be specified for every non-optional input parameter. The content
of the actual parameter is passed to the input parameter when the call is made. The content of an input parameter for which 'pass by reference' is defined cannot be changed in the function module.
- EXPORTING parameters are output parameters. When the function module
is called, a suitable actual parameter can be specified for every output parameter. The content of an
output parameter that is defined for 'pass by value' is passed to the actual parameter if the function
module is completed without errors. An output parameter that is defined for pass by reference is not initialized when the function module is called.
- CHANGING parameters are input and output parameters. When the function
module is called, a suitable actual parameter must be specified for every non-optional input or output
parameter. When the function module is called, the content of the actual parameter is passed to the
input/output parameter, and when the function module is completed, the content of the input/output parameter is passed to the actual parameter.
Note
The formal parameters of a function module can be registered as global parameters in Function Builder, however this is obsolete.
Exceptions
The exceptions of a function module are defined on the Exceptions tab page in Function Builder. Here exception classes can be selected to define whether
class-based exceptions are declared or
non-class-based exception are defined. Class-based
exceptions are represented in the above syntax by RAISING, and non-class-based exceptions are represented by EXCEPTIONS.
- The addition RAISING is used to declare class-based exceptions that can
be propagated from the function module to the caller. Exceptions in the categories CX_STATIC_CHECK and
CX_DYNAMIC_CHECK must be explicitly declared, otherwise a propagation can lead to an interface violation.
A violation of the interface raises the handleable exception CX_SY_NO_HANDLER. Exceptions of the category
CX_NO_CHECK are always declared implicitly and with the RESUMABLE addition.
The declaration of exceptions of the category CX_STATIC_CHECK is checked statically in the syntax check.
For exceptions of the category CX_DYNAMIC_CHECK, the check is not performed until runtime. In a function
module in which class-based exceptions are declared with the RAISING addition,
the statement CATCH SYSTEM-EXCEPTIONS
cannot be used. Instead, the relevant handleable exceptions should be handled in a TRY control structure.
The RESUMABLE addition declares an exception that can be propagated as a
resumable exception.
This addition has no relevance to a non-resumable exception. The addition does not have any effect on
a non-resumable exception. If a resumable exception is propagated with RAISING
without the addition RESUMABLE, it thus becomes non-resumable. If a superclass is declared as resumable, any subclasses must also be declared as resumable.
- The addition EXCEPTIONS is used to define a list of non-class-based exceptions
that can be raised in the function module using the statements
RAISE or MESSAGE RAISING.
Exceptions defined in this way are (as with formal parameters) bound to the function module and cannot
be propagated. If an exception of this type is raised in a function module, and no return value has
been assigned to it with the homonymous addition EXCEPTIONS of the
CALL FUNCTION statement when the call was made, this leads to a runtime
error. In a function module in whose interface non-class-based exceptions are defined, the statement
RAISE
EXCEPTION or the addition THROW in a
conditional expression cannot be used to raise class-based exceptions.
The Resumable column in Function Builder can be selected to flag a class-based exception as a
resumable exception.
This places the RESUMABLE addition behind RAISING in the syntax above.
Note
For new developments, SAP recommends working with class-based exceptions that are independent of the function module.
Continue
Properties of Interface Parameters