Using subroutine pools for dynamic programming

In this article we'll talk about using subroutine pools for dynamic programming in ABAP. The subroutine pools can be generated by using the following syntax:

GENERATE SUBROUTINE POOL itab NAME prog [error_handling].

This statement generates a temporary subroutine pool . The source code of the subroutine pool is taken from the internal table itab. The generated subroutine pool is stored internally in the current internal mode.

The name with a maximum of 30 digits for the temporary subroutine pool is assigned to the variable prog. The line type for itab must be character type (prior to Release 6.10 flat). A source code line in itab may contain a maximum of 255 characters. The data object prog must also be character type (prior to Release 6.10 flat). In an internal mode, a maximum of 36 temporary subroutine pools may be created. If the source text contained in itab has a syntax error, the subroutine pool is not generated and initialized using prog.

Using the addition error_handling, syntax and generation errors can be analyzed. Syntax errors can either occur in the source code specified in itab or in the include programs included using the statement INCLUDE. Generation errors can occur, among other things, if the program contains errors in the declaration statements that are not recognized during the static syntax check.

In the source code of the subroutine pool, subroutines can be called from all programs that are loaded in the same internal mode by specifying the program name prog using the statement PERFORM. At the first call of a subroutine in the subroutine pool, this is loaded into internal mode, where the event LOAD-OF-PROGRAM is initialized.

Now let's demonstrate in an example in which I am using subroutine pools for fetching data from a dynamic table:

REPORT zravie_gen_subroutine_pool3 MESSAGE-ID zrsp. *Using "REUSE_ALV_LIST_DISPLAY" function dynamically TYPE-POOLS: slis. TABLES : dd02l. DATA : source_table(72) OCCURS 0 WITH HEADER LINE, program_name LIKE sy-cprog, syntax_check_message(128), line_no TYPE i. DATA: gt_fcat TYPE lvc_t_fcat, gt_fcat_main TYPE slis_t_fieldcat_alv. DATA: ref_data TYPE REF TO data. FIELD-SYMBOLS: <gt_outtab> TYPE table. PARAMETERS : tabname LIKE dd02l-tabname DEFAULT 'ZEMP3'. AT SELECTION-SCREEN . SELECT SINGLE tabname FROM dd02l INTO CORRESPONDING FIELDS OF dd02l WHERE tabname = tabname. IF sy-subrc <> 0. MESSAGE e000. ENDIF. START-OF-SELECTION. PERFORM build_table USING tabname. GENERATE SUBROUTINE POOL source_table NAME program_name MESSAGE syntax_check_message LINE line_no. IF sy-subrc <> 0. WRITE : / 'Syntax error,message',syntax_check_message, 'in line no',line_no. EXIT. ENDIF. PERFORM display_table IN PROGRAM (program_name). *&-----------------------------------------------------------------* *& Form build_table *&-----------------------------------------------------------------* FORM build_table USING l_tabname. DATA: lwa_source_table LIKE source_table. APPEND 'REPORT test. ' TO source_table. APPEND 'TABLES :' TO source_table. APPEND l_tabname TO source_table. APPEND '.' TO source_table. APPEND ' DATA : gt_itab like ' TO source_table. APPEND l_tabname TO source_table. APPEND ' occurs 0 with header line. ' TO source_table. APPEND 'form display_table.' TO source_table. APPEND 'SELECT * FROM ' TO source_table. APPEND l_tabname TO source_table. APPEND ' into corresponding fields of table gt_itab. ' TO source_table. APPEND 'CALL FUNCTION ''REUSE_ALV_LIST_DISPLAY'' ' TO source_table. APPEND 'EXPORTING ' TO source_table. APPEND 'I_STRUCTURE_NAME = ' TO source_table. CONCATENATE '''' l_tabname '''' INTO lwa_source_table. APPEND lwa_source_table TO source_table. APPEND 'TABLES ' TO source_table. APPEND 'T_OUTTAB = gt_itab. ' TO source_table. APPEND 'endform.' TO source_table. ENDFORM. " build_table

Note :
A maximum of only 36 subroutine pools can be created in a program.

Ravi Shankar Rajan is a senior developer analyst working for General Mills.

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