Determining internal table structure dynamically

Question

Hi,
I have a number of internal tables in my program which I declare using types. As an example:
TYPES: begin of ty_hierarchy,
               control_id(6)   type c,
               node_id(10)     type c,
               node_name       type bezei40,
               material        type matnr,
               node_level      type prodh_stuf,
               node_parent(10) type c,
            end of ty_hierarchy.
DATA: it_hierarchy type ty_hierarchy occurs 0.
Further down my program I need to determine the structure of internal table IT_HIERARCHY dynamically. Because I have a number of internal tables, I need to determine which internal table is being processed. Therefore it's important that I know the structure of the table that I'm currently processing.
I am aware of CL_ABAP* classes and functions like GET_COMPONENT_LIST. However because I have declared my tables using the TYPE statement the method/function cannot read my table structure correctly. If I changed my declaration to be as below, the method/function work! However I don't want to do this as I use field symbols to reference my internal tables and need to use the TYPE statement.
DATA: begin of ty_hierarchy,
               control_id(6)   type c,
               node_id(10)     type c,
               node_name       type bezei40,
               material        type matnr,
               node_level      type prodh_stuf,
               node_parent(10) type c,
            end of ty_hierarchy.
DATA: begin of it_hierarchy occurs 0.
             include structure ty_hierarchy
DATA: end of it_hierarchy.
Does anyone know on how I can determine my  internal table structure dynamically but still keeping my internal table declarations using TYPE statement?
Any help would be greatly appreciated with reward points .....
Thanks
Liam

Answer 1

Hello Liam
Both the ABAP-OO as well as the FM-based approach described by Eswar work well with your way of defining the itabs. I described three different ways how to get the structure of your itab dynamically:
- directly using the itab
- using a field symbol
- using a data reference
REPORT  zus_sdn_dynamic_itabs.
TYPE-POOLS: abap.
TYPES: BEGIN OF ty_hierarchy,
control_id(6) TYPE c,
node_id(10) TYPE c,
node_name TYPE bezei40,
material TYPE matnr,
node_level TYPE prodh_stuf,
node_parent(10) TYPE c,
END OF ty_hierarchy.
DATA:
  gs_hierarchy    TYPE ty_hierarchy,
  it_hierarchy    TYPE ty_hierarchy OCCURS 0.
DATA:
  gt_comp         TYPE abap_compdescr_tab,
  gs_comp_a       LIKE LINE OF gt_comp,
  gd_type         TYPE abap_typekind,
  gs_comp    TYPE rstrucinfo,
  it_comp TYPE TABLE OF rstrucinfo.
DATA:
  go_struct    TYPE REF TO cl_abap_structdescr,
  go_table     TYPE REF TO cl_abap_tabledescr,
  gdo_data     TYPE REF TO data.
FIELD-SYMBOLS:
  <gt_itab>    TYPE table.
START-OF-SELECTION.
  GET REFERENCE OF it_hierarchy INTO gdo_data.
  ASSIGN gdo_data->* TO <gt_itab>.
* (1) Describe directly by using the itab
*  go_table  ?= cl_abap_structdescr=>describe_by_data( it_hierarchy ).
* (2) Describe indirectly by using field symbol
*  go_table  ?= cl_abap_structdescr=>describe_by_data( <gt_itab> ).
* (3) Describe by data reference to itab
  go_table  ?= cl_abap_structdescr=>describe_by_data_ref( gdo_data ).
  go_struct ?= go_table->get_table_line_type( ).
  WRITE: / 'ABAP-OO Version:'.
  gt_comp = go_struct->components.
  LOOP AT gt_comp INTO gs_comp_a.
    WRITE: / gs_comp_a-name,
             gs_comp_a-length,
             gs_comp_a-type_kind,
             gs_comp_a-decimals.
  ENDLOOP.
  SKIP 2.
  CALL FUNCTION 'GET_COMPONENT_LIST'
    EXPORTING
      program    = sy-repid
      fieldname  = 'GS_HIERARCHY'
    TABLES
      components = it_comp.
  WRITE: / 'Function Module Version:'.
  LOOP AT it_comp INTO gs_comp.
    WRITE: / gs_comp-compname,
             gs_comp-level,
             gs_comp-leng,
             gs_comp-type,
             gs_comp-olen,
             gs_comp-decs.
  ENDLOOP.
END-OF-SELECTION.
Regards
  Uwe