OCCURS 0 和 TYPE STANDARD TABLE 有什么区别

Question

I am new to ABAP, and I am creating ALV using FM 'REUSE_ALV_FIELDCATALOG_MERGE' and 'REUSE_ALV_GRID_DISPLAY'.

It is working when I defined internal table IT_MARD using obsolete occurs 0 definition. But I am getting Exception condition "NO_FIELDCATALOG_AVAILABLE" raised, when I defined internal table using type standard table . Could you please explain difference between these two definition and why it is not working in the latter case. The following is the code.

REPORT  ztest_fieldcatalog3.
TYPE-POOLS:slis.
*Semi Automatic Fieldcatalog Generation.
*DATA: BEGIN OF IT_MARD OCCURS 0,
*        MATNR LIKE MARD-MATNR,
*        WERKS LIKE MARD-WERKS,           ""
*        LGORT LIKE MARD-LGORT,
*        PSTAT LIKE MARD-PSTAT,
*      END OF IT_MARD.

TYPES: BEGIN OF ty_mard,
        matnr type mard-matnr,
        werks type mard-werks,
        lgort type mard-lgort,
        pstat type mard-pstat,
      END OF ty_mard.

DATA: IT_MARD TYPE STANDARD TABLE OF ty_mard.


"Use function module create  Fieldcat.
DATA:l_program TYPE sy-repid VALUE sy-repid.

DATA:i_fieldcat TYPE slis_t_fieldcat_alv.

SELECT matnr
       werks
       lgort
       pstat
  FROM mard
  INTO CORRESPONDING FIELDS OF TABLE it_mard
  UP TO 100 ROWS.


CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
  EXPORTING
    i_program_name     = l_program
    i_internal_tabname = 'IT_MARD'
    i_inclname         = l_program
    i_bypassing_buffer = 'X'
  CHANGING
    ct_fieldcat        = i_fieldcat[].
IF sy-subrc <> 0.
  MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
          WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
ENDIF.


"Call ALV and pass fieldcatalog and data
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
  EXPORTING
    i_callback_program = l_program
    it_fieldcat        = i_fieldcat
  TABLES
    t_outtab           = it_mard.
IF sy-subrc <> 0.
  MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
          WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
ENDIF.

Answer 1

The difference is that OCCURS creates a table with a header line, while TYPE STANDARD TABLE OF does not (unless you explicitly tell it to). I suppose that the function module is able to guess the structure from a table with a header line, but not a table without a header line. My suggestions would be to

1. use a data dictionary structure instead of a local structure - it's easier to maintain and extend later on and
2. don't use the REUSE function modules, but check the CL_SALV_* classes instead since they are officially supported and have a much cleaner API