Understanding Field Symbols in ABAP: A Dynamic Mem...

arijit_dutta · ‎01-26-2024

Field symbols in ABAP are akin to pointers in the C language, offering a dynamic approach to memory allocation. Unlike traditional variables, field symbols do not hold any memory themselves; instead, they serve as pointers to specific memory locations. In this blog post, we will delve into the concept of field symbols, exploring their functionality and benefits within the ABAP programming language.

Field Symbol as a Variable

In the following program, we are assigning (Inline declaration) a field symbol. This means that <v_maktx> does not hold any memory allocation, but it points to the value of MAKTX from the MAKT table. Using field symbols always improves the performance of the program since we are working with dynamic memory.

PARAMETERS: p_matnr TYPE matnr.

DATA dref TYPE REF TO data.
CREATE DATA dref TYPE makt-maktx.
ASSIGN dref->* TO FIELD-SYMBOL(<v_maktx>).

SELECT SINGLE maktx FROM makt INTO <v_maktx>
  WHERE matnr = p_matnr
    AND spras = sy-langu.

IF sy-subrc = 0.
  WRITE: / 'Description-', <v_maktx>.
ENDIF.

Range with Field Symbol

DATA: rtab TYPE RANGE OF mara-matnr,
      wtab LIKE LINE OF rtab.

SELECT matnr FROM mara INTO TABLE @DATA(t_mara)
  WHERE mtart = 'ZFRT'.

IF sy-subrc = 0.
  SORT t_mara.
  wtab-sign   = 'I'.
  wtab-option = 'EQ'.

  LOOP AT t_mara ASSIGNING FIELD-SYMBOL(<w_mara>).
    wtab-low = <w_mara>-matnr.
    APPEND wtab TO rtab.

    WRITE:/ wtab-sign,
          3 wtab-option,
          6 wtab-low.
    CLEAR: wtab-low, <w_mara>.
  ENDLOOP.
ENDIF.

Field Symbol as a Work Area

TYPES: BEGIN OF ts_mara,
         matnr TYPE mara-matnr,
         ernam TYPE mara-ernam,
         mtart TYPE mara-mtart,
         matkl TYPE mara-matkl,
       END OF ts_mara.

PARAMETERS: p_matnr TYPE matnr.

DATA dref TYPE REF TO data.
CREATE DATA dref TYPE ts_mara.
ASSIGN dref->* TO FIELD-SYMBOL(<wa_mara>).

SELECT SINGLE matnr ernam mtart matkl
  FROM mara INTO <wa_mara>
  WHERE matnr = p_matnr.

IF sy-subrc = 0.
  ASSIGN COMPONENT 'MATNR' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<matnr>).
  ASSIGN COMPONENT 'ERNAM' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<ernam>).
  ASSIGN COMPONENT 'MTART' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<mtart>).
  ASSIGN COMPONENT 'MATKL' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<matkl>).
  WRITE: / <matnr>,
           <ernam>,
           <mtart>,
           <matkl>.
ENDIF.

Field Symbol as an Internal Table

TABLES: mara.
TYPES: BEGIN OF ts_mara,
         matnr TYPE mara-matnr,
         ernam TYPE mara-ernam,
         mtart TYPE mara-mtart,
         matkl TYPE mara-matkl,
       END OF ts_mara.

SELECT-OPTIONS s_matnr FOR mara-matnr.

DATA dref TYPE REF TO data.
CREATE DATA dref TYPE TABLE OF ts_mara.
FIELD-SYMBOLS <it_mara> TYPE STANDARD TABLE.
ASSIGN dref->* TO <it_mara>.

SELECT matnr ernam mtart matkl
  FROM mara INTO TABLE <it_mara>
  WHERE matnr IN s_matnr.

IF sy-subrc = 0.
  LOOP AT <it_mara> ASSIGNING FIELD-SYMBOL(<wa_mara>).
    ASSIGN COMPONENT 'MATNR' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<matnr>).
    ASSIGN COMPONENT 'ERNAM' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<ernam>).
    ASSIGN COMPONENT 'MTART' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<mtart>).
    ASSIGN COMPONENT 'MATKL' OF STRUCTURE <wa_mara> TO FIELD-SYMBOL(<matkl>).
    WRITE: / <matnr>,
             <ernam>,
             <mtart>,
             <matkl>.
  ENDLOOP.
ENDIF.

Field Symbol in Multiple Tables

TABLES: ekko.
TYPES: BEGIN OF ts_ekko,
         ebeln TYPE ekko-ebeln,
         lifnr TYPE ekko-lifnr,
       END OF ts_ekko.
DATA wa_ekko TYPE ts_ekko.
FIELD-SYMBOLS <it_ekko> TYPE STANDARD TABLE.

TYPES: BEGIN OF ts_ekpo,
         ebeln TYPE ekpo-ebeln,
         ebelp TYPE ekpo-ebelp,
         matnr TYPE ekpo-matnr,
         werks TYPE ekpo-werks,
         lgort TYPE ekpo-lgort,
         menge TYPE ekpo-menge,
         meins TYPE ekpo-meins,
       END OF ts_ekpo.
DATA wa_ekpo TYPE ts_ekpo.
FIELD-SYMBOLS <it_ekpo> TYPE STANDARD TABLE.

TYPES: BEGIN OF ts_lfa1,
         lifnr TYPE lfa1-lifnr,
         name1 TYPE lfa1-name1,
       END OF ts_lfa1.
DATA wa_lfa1 TYPE ts_lfa1.
FIELD-SYMBOLS <it_lfa1> TYPE STANDARD TABLE.

TYPES: BEGIN OF ts_makt,
         matnr TYPE makt-matnr,
         spras TYPE makt-spras,
         maktx TYPE makt-maktx,
       END OF ts_makt.
DATA wa_makt TYPE ts_makt.
FIELD-SYMBOLS <it_makt> TYPE STANDARD TABLE.

TYPES: BEGIN OF ts_out,
         ebeln TYPE ekpo-ebeln,
         ebelp TYPE ekpo-ebelp,
         matnr TYPE ekpo-matnr,
         maktx TYPE makt-maktx,
         werks TYPE ekpo-werks,
         lgort TYPE ekpo-lgort,
         menge TYPE ekpo-menge,
         meins TYPE ekpo-meins,
         lifnr TYPE ekko-lifnr,
         name1 TYPE lfa1-name1,
       END OF ts_out.
DATA wa_out TYPE ts_out.
FIELD-SYMBOLS <it_out> TYPE STANDARD TABLE.

DATA: dref TYPE REF TO data.
FIELD-SYMBOLS <where> TYPE any.

INITIALIZATION.
  SELECT-OPTIONS s_ebeln FOR ekko-ebeln.

START-OF-SELECTION.

  CREATE DATA dref TYPE TABLE OF ts_ekko.
  ASSIGN dref->* TO <it_ekko>.
  SELECT ebeln lifnr
    FROM ekko INTO TABLE <it_ekko>
    WHERE ebeln IN s_ebeln.

  IF sy-subrc = 0.
    CREATE DATA dref TYPE TABLE OF ts_ekpo.
    ASSIGN dref->* TO <it_ekpo>.
    ASSIGN 'ebeln = <it_ekko>-ebeln' TO <where>.

    SELECT ebeln ebelp matnr werks
           lgort menge meins
      FROM ekpo INTO TABLE <it_ekpo>
      FOR ALL ENTRIES IN <it_ekko>
      WHERE (<where>).

    IF sy-subrc = 0.
      CREATE DATA dref TYPE TABLE OF ts_makt.
      ASSIGN dref->* TO <it_makt>.
      ASSIGN 'matnr = <it_ekpo>-matnr' TO <where>.

      SELECT matnr spras maktx
        FROM makt INTO TABLE <it_makt>
        FOR ALL ENTRIES IN <it_ekpo>
        WHERE (<where>)
          AND spras = sy-langu.
    ENDIF.

    CREATE DATA dref TYPE TABLE OF ts_lfa1.
    ASSIGN dref->* TO <it_lfa1>.
    ASSIGN 'lifnr = <it_ekko>-lifnr' TO <where>.

    SELECT lifnr name1
      FROM lfa1 INTO TABLE <it_lfa1>
      FOR ALL ENTRIES IN <it_ekko>
      WHERE (<where>).
  ENDIF.

  SORT: <it_ekpo> BY ('EBELN'),
        <it_ekko> BY ('EBELN'),
        <it_makt> BY ('MATNR'),
        <it_lfa1> BY ('LIFNR').

  IF <it_ekpo> IS ASSIGNED.
    CREATE DATA dref TYPE TABLE OF ts_out.
    ASSIGN dref->* TO <it_out>.
    LOOP AT <it_ekpo> INTO wa_ekpo.
      wa_out-ebeln = wa_ekpo-ebeln.
      wa_out-ebelp = wa_ekpo-ebelp.
      wa_out-matnr = wa_ekpo-matnr.
      wa_out-werks = wa_ekpo-werks.
      wa_out-lgort = wa_ekpo-lgort.
      wa_out-menge = wa_ekpo-menge.
      wa_out-meins = wa_ekpo-meins.

      IF <it_ekko> IS ASSIGNED.
        READ TABLE <it_ekko> INTO wa_ekko
        WITH KEY ('EBELN') = wa_ekpo-ebeln
        BINARY SEARCH.

        IF sy-subrc = 0 AND <it_lfa1> IS ASSIGNED.
          READ TABLE <it_lfa1> INTO wa_lfa1
          WITH KEY ('LIFNR') = wa_ekko-lifnr
          BINARY SEARCH.

          IF sy-subrc = 0.
            wa_out-lifnr = wa_lfa1-lifnr.
            wa_out-name1 = wa_lfa1-name1.
          ENDIF.
        ENDIF.
      ENDIF.

      IF <it_makt> IS ASSIGNED.
        READ TABLE <it_makt> INTO wa_makt
        WITH KEY ('MATNR') = wa_ekpo-matnr
        BINARY SEARCH.
        IF sy-subrc = 0.
          wa_out-maktx = wa_makt-maktx.
        ENDIF.
      ENDIF.

      APPEND wa_out TO <it_out>.
      CLEAR: wa_out, wa_makt, wa_ekko, wa_ekpo, wa_lfa1.
    ENDLOOP.
  ENDIF.

  IF <it_out> IS ASSIGNED.
    WRITE: /  'PO',
           15 'Item',
           24 'Material',
           40 'Description',
           75 'Plant',
           81 'S.Loc.',
           87 'Qty',
          105 'UoM',
          110 'Vendor',
          121 'Name'.
    ULINE.
    LOOP AT <it_out> INTO wa_out.
      WRITE: /  wa_out-ebeln,
             15 wa_out-ebelp,
             24 wa_out-matnr,
             40 wa_out-maktx,
             75 wa_out-werks,
             81 wa_out-lgort,
             87 wa_out-menge,
            105 wa_out-meins,
            110 wa_out-lifnr,
            121 wa_out-name1.
    ENDLOOP.
  ENDIF.

Field Symbol modifies ITAB automatically

TABLES: ekbe.
TYPES: BEGIN OF ts_ekbe,
         ebeln TYPE ekbe-ebeln,
         ebelp TYPE ekbe-ebelp,
         zekkn TYPE ekbe-zekkn,
         vgabe TYPE ekbe-vgabe,
         gjahr TYPE ekbe-gjahr,
         belnr TYPE ekbe-belnr,
         buzei TYPE ekbe-buzei,
         bwart TYPE ekbe-bwart,
         budat TYPE ekbe-budat,
         menge TYPE ekbe-menge,
         matnr TYPE ekbe-matnr,
         werks TYPE ekbe-werks,
         maktx TYPE makt-maktx,
       END OF ts_ekbe.
FIELD-SYMBOLS: <wa_ekbe> TYPE ts_ekbe,
               <it_ekbe> TYPE STANDARD TABLE.

TYPES: BEGIN OF ts_makt,
         matnr TYPE makt-matnr,
         spras TYPE makt-spras,
         maktx TYPE makt-maktx,
       END OF ts_makt.
FIELD-SYMBOLS: <wa_makt> TYPE ts_makt,
               <it_makt> TYPE STANDARD TABLE.

DATA: dref    TYPE REF TO data,
      wa_ekbe TYPE ts_ekbe.

SELECT-OPTIONS s_ebeln FOR ekbe-ebeln.

START-OF-SELECTION.
  CREATE DATA dref TYPE TABLE OF ts_ekbe.
  ASSIGN dref->* TO <it_ekbe>.
  SELECT ebeln ebelp zekkn vgabe
         gjahr belnr buzei bwart
         budat menge matnr werks
    FROM ekbe INTO TABLE <it_ekbe>
    WHERE ebeln IN s_ebeln
      AND matnr NE ' '.

  IF sy-subrc = 0.
    CREATE DATA dref TYPE TABLE OF ts_makt.
    ASSIGN dref->* TO <it_makt>.
    ASSIGN 'matnr = <it_ekbe>-matnr' TO FIELD-SYMBOL(<matnr>).
    SELECT matnr spras maktx
      FROM makt INTO TABLE <it_makt>
      FOR ALL ENTRIES IN <it_ekbe>
      WHERE (<matnr>).

    IF sy-subrc = 0.
      SORT <it_makt> BY ('MATNR').
    ENDIF.
  ENDIF.

  WRITE: / 'PO',
        12 'Item',
        18 'Material Doc.',
        32 'Year',
        38 'Movement',
        48 'Date',
        60 '        Quantity',
        80 'Material',
       105 'Description'.
  ULINE.

  IF <it_ekbe> IS ASSIGNED.
    LOOP AT <it_ekbe> ASSIGNING <wa_ekbe>.

      IF <it_makt> IS ASSIGNED.
        READ TABLE <it_makt> ASSIGNING <wa_makt>
        WITH KEY ('MATNR') = <wa_ekbe>-matnr
        BINARY SEARCH.
        IF sy-subrc = 0.
          <wa_ekbe>-maktx = <wa_makt>-maktx.
        ENDIF.
      ENDIF.

      wa_ekbe = <wa_ekbe>.
      WRITE: / wa_ekbe-ebeln,
            12 wa_ekbe-ebelp,
            18 wa_ekbe-belnr,
            32 wa_ekbe-gjahr,
            38 wa_ekbe-bwart,
            48 wa_ekbe-budat,
            60 wa_ekbe-menge,
            80 wa_ekbe-matnr,
           105 wa_ekbe-maktx.
    ENDLOOP.
  ENDIF.

Field Symbol using Object Oriented

TABLES mara.
FIELD-SYMBOLS: <it_mara> TYPE STANDARD TABLE,
               <it_makt> TYPE STANDARD TABLE.

INITIALIZATION.
  SELECT-OPTIONS s_matnr FOR mara-matnr.

CLASS mat DEFINITION.
  PUBLIC SECTION.
    TYPES: BEGIN OF ts_mara,
             matnr TYPE mara-matnr,
             mtart TYPE mara-mtart,
             matkl TYPE mara-matkl,
             maktx TYPE makt-maktx,
           END OF ts_mara.
    TYPES: BEGIN OF ts_makt,
             matnr TYPE makt-matnr,
             spras TYPE makt-spras,
             maktx TYPE makt-maktx,
           END OF ts_makt.
    DATA dref TYPE REF TO data.
    METHODS: mara, makt, output.
ENDCLASS.

CLASS mat IMPLEMENTATION.
  METHOD mara.
    CREATE DATA dref TYPE TABLE OF ts_mara.
    ASSIGN dref->* TO <it_mara>.

    SELECT matnr mtart matkl
      FROM mara INTO TABLE <it_mara>
     WHERE matnr IN s_matnr.
  ENDMETHOD.

  METHOD makt.
    IF <it_mara> IS ASSIGNED AND <it_mara> IS NOT INITIAL.
      CREATE DATA dref TYPE TABLE OF ts_makt.
      ASSIGN dref->* TO <it_makt>.
      ASSIGN 'matnr = <it_mara>-matnr' TO FIELD-SYMBOL(<matnr>).

      SELECT matnr spras maktx
        FROM makt INTO TABLE <it_makt>
        FOR ALL ENTRIES IN <it_mara>
        WHERE (<matnr>)
          AND spras = sy-langu.
    ENDIF.
  ENDMETHOD.

  METHOD output.
    FIELD-SYMBOLS: <wa_mara> TYPE ts_mara,
                   <wa_makt> TYPE ts_makt.

    IF <it_makt> IS ASSIGNED.
      SORT <it_makt> BY ('MATNR').
    ENDIF.

    IF <it_mara> IS ASSIGNED.
      LOOP AT <it_mara> ASSIGNING <wa_mara>.

        IF <it_makt> IS ASSIGNED.
          READ TABLE <it_makt> ASSIGNING <wa_makt>
          WITH KEY ('MATNR') = <wa_mara>-matnr
          BINARY SEARCH.
          IF sy-subrc = 0.
            <wa_mara>-maktx = <wa_makt>-maktx.
          ENDIF.
        ENDIF.

        WRITE: / <wa_mara>-mtart,
                 <wa_mara>-matkl,
                 <wa_mara>-maktx,
                 <wa_mara>-matnr.
      ENDLOOP.
    ENDIF.
  ENDMETHOD.
ENDCLASS.

START-OF-SELECTION.
  DATA material TYPE REF TO mat.
  CREATE OBJECT material.
  CALL METHOD: material->mara,
               material->makt,
               material->output.

Field Symbol in Control Break Statement

Using a field symbol instead of a regular work area keeps the table's value unchanged, preventing it from converting into asterisks and zeros in the corresponding fields.

TABLES ekpo.
FIELD-SYMBOLS: <it_ekpo> TYPE STANDARD TABLE.

INITIALIZATION.
  SELECT-OPTIONS s_ebeln FOR ekpo-ebeln.

CLASS pur DEFINITION.
  PUBLIC SECTION.
    TYPES: BEGIN OF ts_ekpo,
             ebeln TYPE ekpo-ebeln,
             ebelp TYPE ekpo-ebelp,
             txz01 TYPE ekpo-txz01,
             ktmng TYPE ekpo-ktmng,
             meins TYPE ekpo-meins,
             netpr TYPE ekpo-netpr,
             peinh TYPE ekpo-peinh,
           END OF ts_ekpo.
    DATA dref TYPE REF TO data.
    METHODS: ekpo, output.
ENDCLASS.

CLASS pur IMPLEMENTATION.
  METHOD ekpo.
    CREATE DATA dref TYPE TABLE OF ts_ekpo.
    ASSIGN dref->* TO <it_ekpo>.

    SELECT ebeln ebelp txz01
           ktmng meins netpr peinh
      FROM ekpo INTO TABLE <it_ekpo>
      WHERE ebeln IN s_ebeln.
  ENDMETHOD.

  METHOD output.
    FIELD-SYMBOLS: <wa_ekpo>  TYPE ts_ekpo,
                   <flag>     TYPE char1,
                   <subtot>   TYPE any,
                   <subprice> TYPE any,
                   <grandtot> TYPE any,
                   <grandpr>  TYPE any.

    IF <it_ekpo> IS ASSIGNED.
      CREATE DATA dref TYPE p DECIMALS 2.
      ASSIGN dref->* TO <subtot>.
      CREATE DATA dref TYPE p DECIMALS 2.
      ASSIGN dref->* TO <grandtot>.
      CREATE DATA dref TYPE p DECIMALS 2.
      ASSIGN dref->* TO <subprice>.
      CREATE DATA dref TYPE p DECIMALS 2.
      ASSIGN dref->* TO <grandpr>.
      CREATE DATA dref TYPE char1.
      ASSIGN dref->* TO <flag>.

      LOOP AT <it_ekpo> ASSIGNING <wa_ekpo>.

        AT NEW ('EBELN').
          <flag> = 'X'.
        ENDAT.

        IF <flag> = 'X'.
          WRITE: / <wa_ekpo>-ebeln,
               12  <wa_ekpo>-ebelp,
               20  <wa_ekpo>-txz01,
               45  <wa_ekpo>-ktmng,
               60  <wa_ekpo>-meins,
               65  <wa_ekpo>-netpr,
               80  <wa_ekpo>-peinh.

        ELSE.
          WRITE: /12 <wa_ekpo>-ebelp,
                 20  <wa_ekpo>-txz01,
                 45  <wa_ekpo>-ktmng,
                 60  <wa_ekpo>-meins,
                 65  <wa_ekpo>-netpr,
                 80  <wa_ekpo>-peinh.
        ENDIF.

        <subtot>   = <subtot>   + <wa_ekpo>-ktmng.
        <grandtot> = <grandtot> + <wa_ekpo>-ktmng.
        <subprice> = <subprice> + <wa_ekpo>-netpr.
        <grandpr>  = <grandpr>  + <wa_ekpo>-netpr.

        AT END OF ('EBELN').
          WRITE: / '==================================================',
                 / 'Subtotal',
                 50 <subtot>,
                 70 <subprice>.
          CLEAR: <subtot>, <subprice>.
        ENDAT.

        AT LAST.
          ULINE.
          WRITE: / 'Grand Total',
                 50 <grandtot>,
                 70 <grandpr>.
        ENDAT.

        CLEAR <flag>.
      ENDLOOP.
    ENDIF.
  ENDMETHOD.
ENDCLASS.

START-OF-SELECTION.
  DATA po TYPE REF TO pur.
  CREATE OBJECT po.
  CALL METHOD: po->ekpo,
               po->output.

Object Oriented ALV using Field Symbol

TABLES ekpo.
FIELD-SYMBOLS: <it_ekpo>   TYPE STANDARD TABLE,
               <it_out>    TYPE STANDARD TABLE,
               <it_fcat>   TYPE STANDARD TABLE,
               <wa_layout> TYPE lvc_s_layo.
DATA: obj_con TYPE REF TO cl_gui_custom_container,
      obj_alv TYPE REF TO cl_gui_alv_grid.

INITIALIZATION.
  SELECT-OPTIONS s_ebeln FOR ekpo-ebeln.

CLASS pur DEFINITION.
  PUBLIC SECTION.
    TYPES: BEGIN OF ts_ekpo,
             ebeln TYPE ekpo-ebeln,
             ebelp TYPE ekpo-ebelp,
             txz01 TYPE ekpo-txz01,
             ktmng TYPE ekpo-ktmng,
             meins TYPE ekpo-meins,
             netpr TYPE ekpo-netpr,
             peinh TYPE ekpo-peinh,
           END OF ts_ekpo.
    DATA dref TYPE REF TO data.
    METHODS: ekpo, output, field_catalog.
ENDCLASS.

CLASS pur IMPLEMENTATION.
  METHOD ekpo.
    CREATE DATA dref TYPE TABLE OF ts_ekpo.
    ASSIGN dref->* TO <it_ekpo>.

    SELECT ebeln ebelp txz01
           ktmng meins netpr peinh
      FROM ekpo INTO TABLE <it_ekpo>
      WHERE ebeln IN s_ebeln.
  ENDMETHOD.

  METHOD output.
    FIELD-SYMBOLS: <wa_out>  TYPE ts_ekpo,
                   <wa_ekpo> TYPE ts_ekpo.

    IF <it_ekpo> IS ASSIGNED.
      CREATE DATA dref TYPE ts_ekpo.
      ASSIGN dref->* TO <wa_out>.
      CREATE DATA dref TYPE TABLE OF ts_ekpo.
      ASSIGN dref->* TO <it_out>.

      LOOP AT <it_ekpo> ASSIGNING <wa_ekpo>.

        AT NEW ('EBELN').
          <wa_out>-ebeln = <wa_ekpo>-ebeln.
        ENDAT.

        <wa_out>-ebelp = <wa_ekpo>-ebelp.
        <wa_out>-txz01 = <wa_ekpo>-txz01.
        <wa_out>-ktmng = <wa_ekpo>-ktmng.
        <wa_out>-meins = <wa_ekpo>-meins.
        <wa_out>-netpr = <wa_ekpo>-netpr.
        <wa_out>-peinh = <wa_ekpo>-peinh.

        APPEND <wa_out> TO <it_out>.
      ENDLOOP.
    ENDIF.
  ENDMETHOD.

  METHOD field_catalog.
    DATA lv_col TYPE i VALUE IS INITIAL.
    FIELD-SYMBOLS <wa_fcat> TYPE lvc_s_fcat.
    CREATE DATA dref TYPE lvc_s_fcat.
    ASSIGN dref->* TO <wa_fcat>.

    CREATE DATA dref TYPE TABLE OF lvc_s_fcat.
    ASSIGN dref->* TO <it_fcat>.

    lv_col = lv_col + 1.
    <wa_fcat>-col_pos   = lv_col.
    <wa_fcat>-fieldname = 'EBELN'.
    <wa_fcat>-reptext   = 'Purchase Order'.
    <wa_fcat>-no_zero   = 'X'.
    APPEND <wa_fcat> TO <it_fcat>.

    lv_col = lv_col + 1.
    <wa_fcat>-col_pos   = lv_col.
    <wa_fcat>-fieldname = 'EBELP'.
    <wa_fcat>-reptext   = 'Item'.
    APPEND <wa_fcat> TO <it_fcat>.

    lv_col = lv_col + 1.
    <wa_fcat>-col_pos   = lv_col.
    <wa_fcat>-fieldname = 'TXZ01'.
    <wa_fcat>-reptext   = 'Description'.
    APPEND <wa_fcat> TO <it_fcat>.

    lv_col = lv_col + 1.
    <wa_fcat>-col_pos   = lv_col.
    <wa_fcat>-fieldname = 'KTMNG'.
    <wa_fcat>-reptext   = 'Quantity'.
    APPEND <wa_fcat> TO <it_fcat>.

    lv_col = lv_col + 1.
    <wa_fcat>-col_pos   = lv_col.
    <wa_fcat>-fieldname = 'MEINS'.
    <wa_fcat>-reptext   = 'UoM'.
    APPEND <wa_fcat> TO <it_fcat>.

    lv_col = lv_col + 1.
    <wa_fcat>-col_pos   = lv_col.
    <wa_fcat>-fieldname = 'NETPR'.
    <wa_fcat>-reptext   = 'Price'.
    APPEND <wa_fcat> TO <it_fcat>.

    CREATE DATA dref TYPE lvc_s_layo.
    ASSIGN dref->* TO <wa_layout>.
    <wa_layout>-zebra      = 'X'.
    <wa_layout>-cwidth_opt = 'X'.
  ENDMETHOD.
ENDCLASS.

START-OF-SELECTION.
  DATA po TYPE REF TO pur.
  CREATE OBJECT po.
  SET SCREEN 0100.
  CALL METHOD: po->ekpo,
               po->output,
               po->field_catalog.

*&---------------------------------------------------------------------*
*&      Module  STATUS_0100  OUTPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
MODULE status_0100 OUTPUT.
  SET PF-STATUS 'PF_100'.
  SET TITLEBAR 'T_100'.

  IF <wa_layout> IS ASSIGNED AND
     <it_out>    IS ASSIGNED AND
     <it_fcat>   IS ASSIGNED.

    IF obj_con IS INITIAL.
      CREATE OBJECT obj_con
        EXPORTING
          container_name              = 'ZSR_TEST'
        EXCEPTIONS
          cntl_error                  = 1
          cntl_system_error           = 2
          create_error                = 3
          lifetime_error              = 4
          lifetime_dynpro_dynpro_link = 5
          OTHERS                      = 6.
    ENDIF.

    CREATE OBJECT obj_alv
      EXPORTING
        i_parent          = obj_con
      EXCEPTIONS
        error_cntl_create = 1
        error_cntl_init   = 2
        error_cntl_link   = 3
        error_dp_create   = 4
        OTHERS            = 5.

    CALL METHOD obj_alv->set_table_for_first_display
      EXPORTING
        i_save                        = 'A'
        i_default                     = 'X'
        is_layout                     = <wa_layout>
      CHANGING
        it_outtab                     = <it_out>
        it_fieldcatalog               = <it_fcat>
      EXCEPTIONS
        invalid_parameter_combination = 1
        program_error                 = 2
        too_many_lines                = 3
        OTHERS                        = 4.
  ENDIF.

ENDMODULE.
*&---------------------------------------------------------------------*
*&      Module  USER_COMMAND_0100  INPUT
*&---------------------------------------------------------------------*
*       text
*----------------------------------------------------------------------*
MODULE user_command_0100 INPUT.

  CASE sy-ucomm.
    WHEN 'BACK'.
      LEAVE TO SCREEN 0.
    WHEN 'EXIT'.
      LEAVE PROGRAM.
  ENDCASE.

ENDMODULE.

Conclusion

Field symbols in ABAP offer a powerful mechanism for dynamic memory allocation and data manipulation. By understanding their role and capabilities, developers can leverage field symbols to enhance the flexibility and efficiency of their ABAP programs. Embracing the dynamic nature of field symbols opens up new possibilities for handling complex data scenarios and adapting to changing requirements in the world of ABAP programming.

This blog post provides a comprehensive overview of field symbols in ABAP, highlighting their dynamic memory allocation capabilities and practical applications in programming. By embracing the dynamic nature of field symbols, developers can enhance their ability to manage and manipulate data effectively within the ABAP environment.

Sandra_Rossi · ‎01-27-2024

This blog post is a little bit misleading, field symbols are not used to do memory allocation. It's the statement CREATE DATA which does dynamic "memory allocation". In ABAP, CREATE DATA is not called "memory allocation" (this term is never used, but at least C developers will understand), it's called creating a data object dynamically (i.e. at runtime), the data object ("memory allocation") is pointed by a data reference.

A field symbol is needed only in the context of untyped data references.

You may use CREATE DATA without field symbols if you use typed data references.

A field symbol is more often used to be a pointer to an existing variable or part of a variable rather than a pointer to an untyped data reference.

Notes:

->* is called the "dereferencement operator" (of a data reference).
All your examples use CREATE DATA for no good reason, programs always use named variables (DATA, not CREATE DATA). The classic use of CREATE DATA is with a dynamic type or with RTTS which you don't mention.
You can make your post more attractive by formatting your code this way, which is much better as you can see below.

PARAMETERS: p_matnr TYPE matnr.

DATA dref TYPE REF TO data.
CREATE DATA dref TYPE makt-maktx.
ASSIGN dref->* TO FIELD-SYMBOL(<v_maktx>).

SELECT SINGLE maktx FROM makt INTO <v_maktx>
  WHERE matnr = p_matnr
    AND spras = sy-langu.

IF sy-subrc = 0.
  WRITE: / 'Description-', <v_maktx>.
ENDIF.

ennowulff · ‎02-12-2024

@arijit_dutta This is a very good example on how to NOT use field-symbols.

As @Sandra_Rossi already mentioned: You use data references and field-symbols for no reason. This makes the code unneccessarily complex and hard to maintain.

matt · ‎02-12-2024

TABLES is an obsolete statement.

Florian · ‎02-12-2024

Maybe I don't get the information shared here.. but what you need more to know about field-symbals than that --> https://help.sap.com/doc/abapdocu_751_index_htm/7.51/en-US/index.htm