CONSTANTS: BEGIN OF gc_const_struct,
             comp1 TYPE string VALUE 'component1',
             comp2 TYPE string VALUE 'component2',
             comp3 TYPE string VALUE 'component3',
             comp4 TYPE string VALUE 'component4',
           END OF gc_const_struct.


" Get the components of the structure and their number
DATA(lt_components) = CAST cl_abap_structdescr( cl_abap_typedescr=>describe_by_data( gc_const_struct  ) )->get_components( ).
DATA(lv_num_of_components) = lines( lt_components ).


" Iterate over the components of the structure
" Variant (1) - Iterate over components using loop index
WHILE sy-index <= lv_num_of_components.

  ASSIGN COMPONENT sy-index OF STRUCTURE gc_const_struct  TO FIELD-SYMBOL(<fs_comp_value1>).
  IF <fs_comp_value1> IS NOT ASSIGNED.
    EXIT.
  ELSE.
    WRITE / |Component: { <fs_comp_value1> } |.
  ENDIF.
ENDWHILE.

WRITE / '-------------------------------------'.

" Variant (2) - Directly iterate over component table using LOOP statement
LOOP AT lt_components ASSIGNING FIELD-SYMBOL(<fs_comp>).

  ASSIGN COMPONENT <fs_comp>-name OF STRUCTURE gc_const_struct  TO FIELD-SYMBOL(<fs_comp_value2>).
  IF <fs_comp_value2> IS NOT ASSIGNED.
    EXIT.
  ELSE.
    WRITE / |Component: { <fs_comp_value2> } |.
  ENDIF.
ENDLOOP.