SAP MULTIPLE USE INCLUDE - Guide
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GUIDELINE 4.15
Multiple Use of Include Programs
ABAP_BACKGROUND
From a technical point of view, it is possible to use an include program multiple times by integrating it more than once into a master program or different master programs.
ABAP_RULE
Use an include program for the modularization of exactly one master program. It must not be integrated into multiple different master programs. Also, an include program should only be integrated once within a master program.
ABAP_DETAILS
The multiple use of include programs is highly problematic conceptually. This particularly concerns the use of include programs for the reuse of:
We strongly recommended using only suitable means for reuse, such as global classes or interfaces, for the reasons specified in the following sections.
The integration of an include program into several master programs dramatically restricts the maintainability both of the include program itself and of the master programs using it. Changes to such an include program can be unproblematic in the context of selected master programs, but can make other master programs syntactically incorrect at the same time. This is particularly critical for master programs that integrate include programs that were developed in other systems.
If master programs that use shared include programs are executed at the same time, these include programs must be loaded multiple times by the ABAP runtime environment, which increases memory consumption. In the past, include programs were used multiple times for the central definition of constants, for example. Today, you should use a global interface or global class for this purpose. Because it is loaded only once, the memory consumption does not increase with every new use as it does with any multiple use of include programs.
The memory consumption also increases if an include program is used multiple times within one master program (for example, through i ntegration into the source code of multiple function modules of a function group or into the source code of multiple methods of a class) because this expands the master program unnecessarily. When using centrally defined,
Like source code files in other programming environments, include programs are integrated into a master program as pure text and without any semantics. The semantics only emerge in the context of the master program and the position where the include program is integrated. Consequently, especially class definitions that are integrated into different master programs by using an include program result in different technical classes whose objects have different reference types and cannot be exchanged between the master programs.
Bad example
The following source code shows an include program that contains declarations of constants intended for use in multiple programs. Ac cording to the above rule, such a procedure is no longer permitted.
*<(> <)> Include Z_ORDERS_OF_MAGNITUDE
*<(> <)>---------------------------------------------*
CONSTANTS:
mega TYPE p DECIMALS 6 VALUE '1000000.0',
kilo TYPE p DECIMALS 6 VALUE '1000.0',
milli TYPE p DECIMALS 6 VALUE '0.001',
micro TYPE p DECIMALS 6 VALUE '0.000001'.
Good example
The following source code shows the same declarations of constants as in the above example, but this time in a global class suitable for reuse. Here, a corresponding ABAP Unit test method would even be possible that checks the consistency of the constants.
PUBLIC SECTION.
CONSTANTS:
mega TYPE p DECIMALS 6 VALUE '1000000.0',
kilo TYPE p DECIMALS 6 VALUE '1000.0',
milli TYPE p DECIMALS 6 VALUE '0.001',
micro TYPE p DECIMALS 6 VALUE '0.000001'.
ENDCLASS.
