读取内表的Field Name

TYPES:
BEGIN OF my_struct,
comp_a TYPE i,
comp_b TYPE f,
END OF my_struct.

DATA:
my_data TYPE my_struct,
descr_ref TYPE REF TO cl_abap_structdescr.

DATA: BEGIN OF itab OCCURS 0 ,
        f1 ,
        f2 ,
      END OF itab.

FIELD-SYMBOLS:
TYPE abap_compdescr.

START-OF-SELECTION.
  descr_ref ?= cl_abap_typedescr=>describe_by_data( my_data ).
  LOOP AT descr_ref->components ASSIGNING .
    WRITE: / -name.
  ENDLOOP.

  descr_ref ?= cl_abap_typedescr=>describe_by_data( itab ).
  LOOP AT descr_ref->components ASSIGNING .
    WRITE: / -name.
  ENDLOOP.