How to point to the next line of aninternal table

Question

Hello experts,i am studying webdynpro abap, i am trying to point to the last line of an internal table, then add 1, in order to insert just in that position a new line by calling the function module ZFM_INSERT_CANDIDATE,neither the method INSERT_CANDIDATE nor the function module ZFM_INSERT_CANDIDATE  throws any error,.
The method testing just dont do anything. what could i try? the source is the following, :
method INSERT_CANDIDATE.
data: itab TYPE ztable_type,
t_line type zperson-id_person.
data: COUNTLINES type i.
"itab = me->SELECT_CANDIDATE().T_LINE = LINES( ITAB ) + 1.
DESCRIBE TABLE ITAB LINES COUNTLINES .
COUNTLINES = COUNTLINES + 1.
itab =  me->SELECT_CANDIDATE( ).T_LINE =  COUNTLINES .
   try.
     call FUNCTION 'ZFM_INSERT_CANDIDATE'
     EXPORTING
       id_candidate = t_line
       firstname = firstname
       lastname = lastname
       age = age
       telephone = telephone
       id_country = id_country.
     ENDTRY.
endmethod.
tnkx in advanced

Answer 1

Hello Tashi, you are right , so i am pasting some images:
method select_cadidate:
FunctionMod  ZFM_insert_candidate:
FUNCTION ZFM_INSERT_CANDIDATE.
*"*"Local Interface:
*"  IMPORTING
*"     VALUE(ID_CANDIDATE) TYPE  ZPERSON-ID_PERSON
*"     VALUE(FIRSTNAME) TYPE  ZPERSON-FIRSTNAME
*"     VALUE(LASTNAME) TYPE  ZPERSON-LASTNAME
*"     VALUE(AGE) TYPE  ZPERSON-AGE
*"     VALUE(TELEPHONE) TYPE  ZPERSON-TELEPHONE
*"     VALUE(ID_COUNTRY) TYPE  ZPERSON-ID_COUNTRY
*"  EXCEPTIONS
*"      ZCX_EXCEPTION_T1OO_TXT
DATA wa_person TYPE Zperson.
wa_person-mandt = sy-mandt.
wa_person-id_person = id_candidate.
wa_person-firstname = firstname.
wa_person-lastname = lastname.
wa_person-age = age.
wa_person-telephone = telephone.
wa_person-id_country = id_country.
TRY.
INSERT into Zperson values wa_person.
IF sy-subrc <> 0.
"RAISE EXCEPTION TYPE ycx_exception_t100_txt
"EXPORTING textid = ycx_exception_t100_txt=>ycx_insert_no_possible.
  WRITE: 'ERROR AL INSERTAR'.
ENDIF.
ENDTRY.
ENDFUNCTION.
If test the FM separately , it works:
Finally, the table: