How to export a reference to a table line from a method?

Question

Hello,
I have a class which has a hashed table as an attribute. I want to retrieve a line from the table using the key and return a reference to the table line. I want changes to the return value of the method to be directly reflected in the table, as if using a local field symbol. I have tried to approaches, neither of which works.
First, I returned a reference to the local field symbol. This dumps, because after returning from the method call, the target of this reference no longer resides on the stack.
Second, I have tried using an export parameter marked as "pass by reference", i. e. without VALUE(). Strangely, this still seems to give me only a copy of the data.
What is the correct way to proceed?
Illustrative pseudo-code follows.
Thanks, Sebastian
*==============================================================
*Possibility 1: (using references)
DATA mt_key_map TYPE zt_entity. " member variable (hash table of zs_entity)
METHODS get
    IMPORTING
      !is_key TYPE zs_key
    EXPORTING
      !er_vt TYPE REF TO zs_entity.
METHOD get.
  FIELD-SYMBOLS: <fs_vt> TYPE zs_entity. 
  READ TABLE mt_key_value WITH KEY key = is_key ASSIGNING <fs_vt>.
  GET REFERENCE OF <fs_vt> INTO er_vt.
ENDMETHOD.     
" Client Code:
  FIELD-SYMBOLS: <fs_vt> TYPE zs_entity. 
  CALL METHOD get
    EXPORTING
      is_key        = is_key
    IMPORTING
      er_vt         = lr_vt.
  ASSIGN lr_vt->* TO <fs_vt>.  " will dump, because the local field symbol
                               " to which lr_vt points is no longer on the stack
  <fs_vt>-value = 'newdata'.       
*==============================================================
*Possibility 2:  (using a structure passed by reference)
DATA mt_key_map TYPE zt_entity. " member variable (hash table of zs_entity)
METHODS get
    IMPORTING
      !is_key TYPE zs_key
    EXPORTING
      !es_vt TYPE zs_entity.  
METHOD get.
  FIELD-SYMBOLS: <fs_vt> TYPE zs_entity. 
  READ TABLE mt_key_map WITH KEY key = is_key ASSIGNING <fs_vt>.
  es_vt = <fs_vt>.
ENDMETHOD.   
" Client Code:
  DATA: ls_vt TYPE zs_entity.
  CALL METHOD get
    EXPORTING
      is_key        = is_key
    IMPORTING
      es_vt         = ls_vt.
  ls_vt-value = 'newdata'.   " will not change the contents of the
                             " table mt_key_value       

Answer 1

In the first approch, try to change the exporting parameter type REF TO DATA.
Try like:
CLASS lcl_test DEFINITION.
  PUBLIC SECTION.
    DATA: t_mara TYPE HASHED TABLE OF mara WITH UNIQUE KEY matnr.
    METHODS:
      constructor,
      get
        IMPORTING
          if_matnr TYPE matnr
        EXPORTING
          ea_mara  TYPE REF TO data.
ENDCLASS.                    "lcl_test DEFINITION
START-OF-SELECTION.
  DATA: lo_test TYPE REF TO lcl_test,
        lr_data TYPE REF TO data.
  FIELD-SYMBOLS: <fa_mara> TYPE ANY,
                 <f_field> TYPE ANY.
  CREATE OBJECT lo_test.
  lo_test->get(
    EXPORTING
      if_matnr = '000000000077000000'   " << Replace Your Material
    IMPORTING
      ea_mara  = lr_data ).
  ASSIGN lr_data->* TO <fa_mara>.
  ASSIGN COMPONENT 'ERSDA' OF STRUCTURE <fa_mara> TO <f_field>.
  <f_field> = space.
  WRITE: 'Done'.
CLASS lcl_test IMPLEMENTATION.
  METHOD constructor.
    SELECT * INTO TABLE t_mara
           FROM mara
           UP TO 10 ROWS.
  ENDMETHOD.                    "constructor
  METHOD get.
    FIELD-SYMBOLS: <lfs_mara> LIKE LINE OF me->t_mara.
    READ TABLE me->t_mara ASSIGNING <lfs_mara> WITH KEY matnr = if_matnr.
    GET REFERENCE OF <lfs_mara> INTO ea_mara.
  ENDMETHOD.                    "get
ENDCLASS.                    "lcl_test IMPLEMENTATION
Regards,
Naimesh Patel