dynamic - 如何使用动态字段名称循环遍历动态 itab 名称？

Question

构造了一个动态内部表，其中表名作为用户的输入字符串，如何循环遍历它？

请找到 MWE:

DATA W_TABNAME TYPE W_TABNAME.
DATA W_DREF TYPE REF TO DATA.
DATA W_WA TYPE REF TO DATA.

FIELD-SYMBOLS <ITAB> TYPE ANY TABLE.
FIELD-SYMBOLS <WA> TYPE ANY.

W_TABNAME = P_TABLE.

CREATE DATA W_DREF TYPE TABLE OF (W_TABNAME).
ASSIGN W_DREF->* TO <ITAB>.

CREATE DATA W_WA LIKE LINE OF <ITAB>.
ASSIGN W_WA->* TO <WA>.

SELECT * FROM (W_TABNAME) INTO TABLE <ITAB>.

LOOP AT <ITAB> INTO <WA>.
  **WRITE:/ <WA>.** ---> how do I fetch the field name here
ENDLOOP. 

Answer 1

结合 vwegert 和 Leelaprasad Kolapalli 的答案:

DATA: lro_structdescr TYPE REF TO cl_abap_structdescr,
      lt_components   TYPE cl_abap_structdescr=>component_table.
 FIELD-SYMBOLS: <ls_comp> LIKE LINE OF lt_components.

   LOOP AT itab ASSIGNING <wa>
      IF lt_components IS INITIAL.  "get columns' names only once.
        lro_structdescr ?= cl_abap_typedescr=>describe_by_data( <wa> ).
        lt_components = lro_structdescr->get_components( ).
      ENDIF.

      DO. "iterate all columns in the row
        ASSIGN COMPONENT sy-index OF STRUCTURE <wa> TO <fs_field>.
        IF sy-subrc <> 0.
          EXIT.
        ENDIF.

        READ TABLE lt_components ASSIGNING <ls_comp> INDEX sy-index.
        "field name: <ls_comp>-name.
        "field value: <fs_field>.
      ENDDO.
   ENDLOOP