ABAP Function Modules: Creating and Using Function Modules

CALL FUNCTION 'FUNCTION_NAME'
  EXPORTING
    param1 = value1
  IMPORTING
    result = lv_result
  CHANGING
    data   = ls_data
  TABLES
    itab   = lt_table
  EXCEPTIONS
    error1 = 1
    error2 = 2
    OTHERS = 3.

IF sy-subrc <> 0.
  " Error handling
ENDIF.

DATA: lv_date_out TYPE sy-datum.

" Calculate date
CALL FUNCTION 'RP_CALC_DATE_IN_INTERVAL'
  EXPORTING
    date      = sy-datum
    days      = 30
    months    = 0
    signum    = '+'
    years     = 0
  IMPORTING
    calc_date = lv_date_out.

WRITE: / 'Date + 30 days:', lv_date_out.

DATA: lv_result TYPE p DECIMALS 2.

CALL FUNCTION 'CONVERSION_EXIT_ALPHA_INPUT'
  EXPORTING
    input  = '123'
  IMPORTING
    output = lv_result
  EXCEPTIONS
    invalid_input = 1
    OTHERS        = 2.

CASE sy-subrc.
  WHEN 0.
    WRITE: / 'Result:', lv_result.
  WHEN 1.
    WRITE: / 'Invalid input'.
  WHEN OTHERS.
    WRITE: / 'Unknown error'.
ENDCASE.

" In SE37 or SE80:
" 1. Create function group: ZFGRP_CUSTOMER
" 2. Create function module: Z_CUSTOMER_GET_BY_ID

FUNCTION z_customer_get_by_id.
*"----------------------------------------------------------------------
*"*"Local Interface:
*"  IMPORTING
*"     VALUE(IV_KUNNR) TYPE KUNNR
*"  EXPORTING
*"     VALUE(ES_CUSTOMER) TYPE KNA1
*"     VALUE(EV_FOUND) TYPE ABAP_BOOL
*"  EXCEPTIONS
*"     CUSTOMER_NOT_FOUND
*"     INVALID_INPUT
*"----------------------------------------------------------------------

  " Input validation
  IF iv_kunnr IS INITIAL.
    RAISE invalid_input.
  ENDIF.

  " Read customer
  SELECT SINGLE * FROM kna1
    WHERE kunnr = @iv_kunnr
    INTO @es_customer.

  IF sy-subrc = 0.
    ev_found = abap_true.
  ELSE.
    ev_found = abap_false.
    RAISE customer_not_found.
  ENDIF.

ENDFUNCTION.


" Calling
DATA: ls_customer TYPE kna1,
      lv_found    TYPE abap_bool.

CALL FUNCTION 'Z_CUSTOMER_GET_BY_ID'
  EXPORTING
    iv_kunnr           = '0000001000'
  IMPORTING
    es_customer        = ls_customer
    ev_found           = lv_found
  EXCEPTIONS
    customer_not_found = 1
    invalid_input      = 2
    OTHERS             = 3.

IF sy-subrc = 0.
  WRITE: / ls_customer-name1.
ENDIF.

" Setting in SE37:
" Attributes -> Processing Type: Remote-Enabled Module

FUNCTION z_rfc_get_sales_data.
*"----------------------------------------------------------------------
*"*"Local Interface:
*"  IMPORTING
*"     VALUE(IV_VKORG) TYPE VKORG
*"     VALUE(IV_DATE_FROM) TYPE SY-DATUM
*"     VALUE(IV_DATE_TO) TYPE SY-DATUM
*"  EXPORTING
*"     VALUE(ET_ORDERS) TYPE ZTT_ORDERS
*"  EXCEPTIONS
*"     NO_DATA_FOUND
*"     INVALID_DATE_RANGE
*"----------------------------------------------------------------------

  " Validate date range
  IF iv_date_from > iv_date_to.
    RAISE invalid_date_range.
  ENDIF.

  " Read data
  SELECT vbeln, erdat, kunnr, netwr
    FROM vbak
    WHERE vkorg = @iv_vkorg
      AND erdat BETWEEN @iv_date_from AND @iv_date_to
    INTO CORRESPONDING FIELDS OF TABLE @et_orders.

  IF sy-subrc <> 0.
    RAISE no_data_found.
  ENDIF.

ENDFUNCTION.


" Remote call
CALL FUNCTION 'Z_RFC_GET_SALES_DATA'
  DESTINATION 'PRD_100'           " RFC Destination
  EXPORTING
    iv_vkorg     = '1000'
    iv_date_from = '20240101'
    iv_date_to   = '20241231'
  IMPORTING
    et_orders    = lt_orders
  EXCEPTIONS
    no_data_found      = 1
    invalid_date_range = 2
    communication_failure = 3 MESSAGE lv_msg
    system_failure        = 4 MESSAGE lv_msg
    OTHERS                = 5.

IF sy-subrc >= 3.
  WRITE: / 'RFC Error:', lv_msg.
ENDIF.

" TABLES is obsolete, but still frequently used
FUNCTION z_process_items.
*"----------------------------------------------------------------------
*"*"Local Interface:
*"  TABLES
*"     IT_ITEMS STRUCTURE ZITEM
*"     ET_RESULTS STRUCTURE ZRESULT
*"----------------------------------------------------------------------

  LOOP AT it_items.
    " Processing
    et_results-id = it_items-id.
    et_results-status = 'OK'.
    APPEND et_results.
  ENDLOOP.

ENDFUNCTION.


" Modern alternative: TYPE for table parameters
FUNCTION z_process_items_new.
*"----------------------------------------------------------------------
*"  IMPORTING
*"     VALUE(IT_ITEMS) TYPE ZTT_ITEMS
*"  EXPORTING
*"     VALUE(ET_RESULTS) TYPE ZTT_RESULTS
*"----------------------------------------------------------------------

  LOOP AT it_items INTO DATA(ls_item).
    APPEND VALUE #( id = ls_item-id status = 'OK' ) TO et_results.
  ENDLOOP.

ENDFUNCTION.

" For asynchronous database changes
FUNCTION z_update_customer IN UPDATE TASK.
*"----------------------------------------------------------------------
*"  IMPORTING
*"     VALUE(IS_CUSTOMER) TYPE KNA1
*"----------------------------------------------------------------------

  MODIFY kna1 FROM is_customer.

ENDFUNCTION.


" Calling
CALL FUNCTION 'Z_UPDATE_CUSTOMER' IN UPDATE TASK
  EXPORTING
    is_customer = ls_customer.

" Commit executes the update
COMMIT WORK AND WAIT.

FUNCTION z_divide_numbers.
*"----------------------------------------------------------------------
*"  IMPORTING
*"     VALUE(IV_DIVIDEND) TYPE I
*"     VALUE(IV_DIVISOR) TYPE I
*"  EXPORTING
*"     VALUE(EV_RESULT) TYPE P
*"  RAISING
*"     ZCX_DIVISION_BY_ZERO
*"----------------------------------------------------------------------

  IF iv_divisor = 0.
    RAISE EXCEPTION TYPE zcx_division_by_zero.
  ENDIF.

  ev_result = iv_dividend / iv_divisor.

ENDFUNCTION.


" Calling with TRY-CATCH
TRY.
    CALL FUNCTION 'Z_DIVIDE_NUMBERS'
      EXPORTING
        iv_dividend = 100
        iv_divisor  = 0
      IMPORTING
        ev_result   = lv_result.

  CATCH zcx_division_by_zero INTO DATA(lx_error).
    WRITE: / lx_error->get_text( ).
ENDTRY.

" TOP-Include of the function group (LZFGRP_CUSTOMERTOP)
FUNCTION-POOL zfgrp_customer.

DATA: gt_cache TYPE HASHED TABLE OF kna1 WITH UNIQUE KEY kunnr.


" Function Module uses global data
FUNCTION z_customer_get_cached.
*"----------------------------------------------------------------------
*"  IMPORTING
*"     VALUE(IV_KUNNR) TYPE KUNNR
*"  EXPORTING
*"     VALUE(ES_CUSTOMER) TYPE KNA1
*"----------------------------------------------------------------------

  " First search in cache
  READ TABLE gt_cache INTO es_customer
    WITH KEY kunnr = iv_kunnr.

  IF sy-subrc <> 0.
    " Load from DB and cache
    SELECT SINGLE * FROM kna1
      WHERE kunnr = @iv_kunnr
      INTO @es_customer.

    IF sy-subrc = 0.
      INSERT es_customer INTO TABLE gt_cache.
    ENDIF.
  ENDIF.

ENDFUNCTION.


" Clear cache
FUNCTION z_customer_clear_cache.
  CLEAR gt_cache.
ENDFUNCTION.

DATA: lv_funcname TYPE funcname VALUE 'Z_CUSTOMER_GET_BY_ID',
      lt_params   TYPE abap_func_parmbind_tab,
      lt_excps    TYPE abap_func_excpbind_tab,
      ls_customer TYPE kna1,
      lv_kunnr    TYPE kunnr VALUE '0000001000'.

" Build parameters
lt_params = VALUE #(
  ( name  = 'IV_KUNNR'
    kind  = abap_func_exporting
    value = REF #( lv_kunnr ) )
  ( name  = 'ES_CUSTOMER'
    kind  = abap_func_importing
    value = REF #( ls_customer ) )
).

lt_excps = VALUE #(
  ( name = 'CUSTOMER_NOT_FOUND' value = 1 )
  ( name = 'OTHERS' value = 99 )
).

" Dynamic call
CALL FUNCTION lv_funcname
  PARAMETER-TABLE lt_params
  EXCEPTION-TABLE lt_excps.

IF sy-subrc = 0.
  WRITE: / ls_customer-name1.
ENDIF.

" In SE37:
" 1. Open function module
" 2. Menu: Function Module -> Test -> Single Test
" 3. Enter parameters
" 4. F8 to execute

" Or programmatically with Unit Test
CLASS ltcl_function_test DEFINITION FOR TESTING
  DURATION SHORT RISK LEVEL HARMLESS.

  PRIVATE SECTION.
    METHODS: test_customer_get FOR TESTING.
ENDCLASS.

CLASS ltcl_function_test IMPLEMENTATION.
  METHOD test_customer_get.
    DATA: ls_customer TYPE kna1,
          lv_found    TYPE abap_bool.

    CALL FUNCTION 'Z_CUSTOMER_GET_BY_ID'
      EXPORTING
        iv_kunnr    = '0000001000'
      IMPORTING
        es_customer = ls_customer
        ev_found    = lv_found
      EXCEPTIONS
        OTHERS      = 1.

    cl_abap_unit_assert=>assert_equals(
      exp = 0
      act = sy-subrc
      msg = 'Function should succeed'
    ).

    cl_abap_unit_assert=>assert_true(
      act = lv_found
      msg = 'Customer should be found'
    ).
  ENDMETHOD.
ENDCLASS.

" In SE37:
" Menu: Goto -> Documentation

" Structured documentation:
" - Short description
" - Parameter documentation
" - Example call
" - Exceptions explained

" Documentation in code (for developers)
FUNCTION z_well_documented.
*"----------------------------------------------------------------------
*" Description:
*"   Calculates the total price including VAT
*"
*" Parameters:
*"   IV_AMOUNT    - Net amount
*"   IV_TAX_RATE  - Tax rate in percent (e.g., 19)
*"   EV_TOTAL     - Gross amount
*"
*" Exceptions:
*"   INVALID_AMOUNT   - Amount is negative
*"   INVALID_TAX_RATE - Tax rate outside 0-100
*"
*" Example:
*"   CALL FUNCTION 'Z_WELL_DOCUMENTED'
*"     EXPORTING iv_amount = 100 iv_tax_rate = 19
*"     IMPORTING ev_total = lv_total.
*"   " lv_total = 119.00
*"----------------------------------------------------------------------
  " Implementation...
ENDFUNCTION.

" Special Function Modules for formatting
" Naming convention: CONVERSION_EXIT_<NAME>_INPUT/OUTPUT

FUNCTION conversion_exit_alpha_input.
*" Add leading zeros
*"  IMPORTING VALUE(INPUT)
*"  EXPORTING VALUE(OUTPUT)

  CALL FUNCTION 'CONVERSION_EXIT_ALPHA_INPUT'
    EXPORTING input  = '1000'
    IMPORTING output = lv_kunnr.
  " lv_kunnr = '0000001000'

ENDFUNCTION.

FUNCTION conversion_exit_alpha_output.
*" Remove leading zeros

  CALL FUNCTION 'CONVERSION_EXIT_ALPHA_OUTPUT'
    EXPORTING input  = '0000001000'
    IMPORTING output = lv_display.
  " lv_display = '1000'

ENDFUNCTION.

" Yes/No Popup
DATA: lv_answer TYPE c LENGTH 1.

CALL FUNCTION 'POPUP_TO_CONFIRM'
  EXPORTING
    titlebar              = 'Confirmation'
    text_question         = 'Do you want to continue?'
    text_button_1         = 'Yes'
    text_button_2         = 'No'
    default_button        = '2'
    display_cancel_button = abap_false
  IMPORTING
    answer                = lv_answer.

IF lv_answer = '1'.
  " Yes selected
ENDIF.


" Text input
DATA: lv_input TYPE string.

CALL FUNCTION 'POPUP_GET_VALUES'
  EXPORTING
    popup_title = 'Input'
  TABLES
    fields      = lt_fields.


" Display message
CALL FUNCTION 'POPUP_TO_DISPLAY_TEXT'
  EXPORTING
    titel     = 'Information'
    textline1 = 'Processing completed.'
    textline2 = '100 records processed.'.

" Function Module for background job
FUNCTION z_batch_process.
*"----------------------------------------------------------------------
*"  IMPORTING
*"     VALUE(IV_DATE) TYPE SY-DATUM
*"----------------------------------------------------------------------

  " Can be executed in background job
  " No dialog calls!

  SELECT * FROM vbak
    WHERE erdat = @iv_date
    INTO TABLE @DATA(lt_orders).

  LOOP AT lt_orders INTO DATA(ls_order).
    " Processing without user interaction
  ENDLOOP.

ENDFUNCTION.


" Schedule as job
SUBMIT zreport_calling_function
  VIA JOB lv_jobname NUMBER lv_jobcount
  AND RETURN.

CLASS zcl_function_wrapper DEFINITION.
  PUBLIC SECTION.
    " Type-safe wrappers for frequently used FMs

    CLASS-METHODS: convert_to_internal
      IMPORTING iv_external       TYPE clike
      RETURNING VALUE(rv_internal) TYPE kunnr.

    CLASS-METHODS: convert_to_external
      IMPORTING iv_internal       TYPE kunnr
      RETURNING VALUE(rv_external) TYPE string.

    CLASS-METHODS: calculate_date
      IMPORTING iv_date          TYPE sy-datum
                iv_days          TYPE i DEFAULT 0
                iv_months        TYPE i DEFAULT 0
                iv_years         TYPE i DEFAULT 0
      RETURNING VALUE(rv_date)   TYPE sy-datum.
ENDCLASS.

CLASS zcl_function_wrapper IMPLEMENTATION.
  METHOD convert_to_internal.
    CALL FUNCTION 'CONVERSION_EXIT_ALPHA_INPUT'
      EXPORTING input  = iv_external
      IMPORTING output = rv_internal.
  ENDMETHOD.

  METHOD convert_to_external.
    CALL FUNCTION 'CONVERSION_EXIT_ALPHA_OUTPUT'
      EXPORTING input  = iv_internal
      IMPORTING output = rv_external.
  ENDMETHOD.

  METHOD calculate_date.
    DATA: lv_sign TYPE c LENGTH 1.

    " Positive or negative
    IF iv_days >= 0 AND iv_months >= 0 AND iv_years >= 0.
      lv_sign = '+'.
    ELSE.
      lv_sign = '-'.
    ENDIF.

    CALL FUNCTION 'RP_CALC_DATE_IN_INTERVAL'
      EXPORTING
        date      = iv_date
        days      = abs( iv_days )
        months    = abs( iv_months )
        signum    = lv_sign
        years     = abs( iv_years )
      IMPORTING
        calc_date = rv_date.
  ENDMETHOD.
ENDCLASS.


" Usage
DATA(lv_kunnr) = zcl_function_wrapper=>convert_to_internal( '1000' ).
DATA(lv_next_month) = zcl_function_wrapper=>calculate_date(
  iv_date   = sy-datum
  iv_months = 1
).