copy from one structure to another copy of the same structure and only overwrite the new items

copy_structure.abap

METHOD copy_structure .
* parameters
* i_new type any
* i_old type any
* final - changing type any

*  copy by component only if the new value is populated else take
*  the existing component
  DATA: _componentno TYPE i   VALUE 0
      .

  FIELD-SYMBOLS: <field_new>       TYPE ANY
               , <field_old>       TYPE ANY
               .

  final  = i_old.

  DO.
    _componentno = _componentno + 1.
    ASSIGN COMPONENT _componentno OF STRUCTURE final  TO <field_old>.
    ASSIGN COMPONENT _componentno OF STRUCTURE i_new  TO <field_new>.

    IF sy-subrc <> 0.
      EXIT.
    ELSE.
      IF <field_old> IS ASSIGNED
        AND <field_new> IS ASSIGNED
        AND <field_new> IS NOT INITIAL.

        <field_old> = <field_new>.
      ENDIF.
    ENDIF.

  ENDDO.

ENDMETHOD.