How to write a Select so that the field list can be easily extended?

[joachimrees1]

(Note: first I thought about asking this question, but now I think I found the answer myself, so this became a blog!

tl;dr: the answer is CDS + extend view! 🙂

)

[I write this from a partners point of view, but it applies to anyone writing code that might be extended in another system down the line].

 

I wrote a cool program to display a material list:

(get data is at the very end)

*&---------------------------------------------------------------------*

*& Report zz_jre_select_enahnce

*&---------------------------------------------------------------------*

*&

*&---------------------------------------------------------------------*

REPORT zz_jre_select_enahnce.



Types: gty_data type mara ,

       gty_tab_data TYPE STANDARD TABLE OF gty_data .



*data, solely for select-options.

data: gso_mara type mara.



*Sel-Screen:

SELECTION-SCREEN BEGIN OF BLOCK sel_opt WITH FRAME TITLE text-t01.

SELECT-Options: so_matnr for gso_mara-matnr.

SELECTION-SCREEN END OF BLOCK sel_opt.



SELECTION-SCREEN BEGIN OF BLOCK mode WITH FRAME TITLE text-t02.

PARAMETERS: pa_disp TYPE flag RADIOBUTTON GROUP mode DEFAULT 'X',

            pa_proc TYPE flag RADIOBUTTON GROUP mode.

 SELECTION-SCREEN END OF BLOCK mode.



CLASS lcl_report DEFINITION.

  PUBLIC SECTION.

    METHODS: display_data CHANGING ct_data TYPE gty_tab_data.

    METHODS: process_data IMPORTING it_data TYPE gty_tab_data.

ENDCLASS.                    "lcl_report DEFINITION



CLASS lcl_report IMPLEMENTATION.

  METHOD process_data.

    FIELD-SYMBOLS: <data> LIKE LINE OF it_data.

    CHECK it_data IS NOT INITIAL.

    LOOP AT it_data ASSIGNING <data>.

*do something

    ENDLOOP.

  ENDMETHOD.                    "process_data



  METHOD display_data.

    DATA: lr_alv          TYPE REF TO cl_salv_table.

    DATA: lr_functions    TYPE REF TO cl_salv_functions_list,

          lr_layout       TYPE REF TO cl_salv_layout,

          ls_key          TYPE salv_s_layout_key.

    TRY.

        CALL METHOD cl_salv_table=>factory

          EXPORTING

            list_display = if_salv_c_bool_sap=>false

          IMPORTING

            r_salv_table = lr_alv

          CHANGING

            t_table      = ct_data.

        ##NO_HANDLER.

      CATCH cx_salv_msg .

    ENDTRY.



    lr_layout = lr_alv->get_layout( ).



    ls_key-report = sy-repid.

    lr_layout->set_key( ls_key ).

    lr_layout->set_default( abap_true ).

    lr_layout->set_save_restriction( if_salv_c_layout=>restrict_none ).



    lr_functions = lr_alv->get_functions( ).

    lr_functions->set_all( abap_true ).



    CALL METHOD lr_alv->display.



  ENDMETHOD.                    "display_data

ENDCLASS.                    "lcl_report IMPLEMENTATION







START-OF-SELECTION.

  PERFORM start_of_selection.



FORM start_of_selection.



  DATA: lt_data TYPE gty_tab_data,

        lo_report TYPE REF TO lcl_report.



*by using a form-routine to get_data we can just use paramters and

*select-options inside.

  PERFORM get_data CHANGING lt_data.



  check lt_data is not initial.



  CREATE OBJECT lo_report.



  CASE abap_true.

    WHEN pa_disp.

      lo_report->display_data( changing ct_data = lt_data ).

    WHEN pa_proc.

      lo_report->process_data( EXPORTING it_data = lt_data ).

  ENDCASE.

ENDFORM.                    "start_of_selection





FORM get_data  CHANGING PT_DATA TYPE gty_tab_data.



select

 matnr,

 ernam,

 ersda

 from mara into CORRESPONDING FIELDS OF table @pt_data UP TO 500 ROWS

  where matnr in @so_matnr

  .

ENDFORM.

 

 

But I also want to give customers the chance to enhance it, adding more fields to the select.

What's the best way to do it?

 

This would be nice but doesn't work:

FORM get_data_static_list  CHANGING PT_DATA TYPE gty_tab_data.



select

 matnr,

 ernam,

 ersda

*[enhancement-spot here would be nice, but is not possibel ]

 from mara into CORRESPONDING FIELDS OF table @pt_data UP TO 500 ROWS

  where matnr in @so_matnr

  .

ENDFORM.

 

Put the whole select into an enhancement-section:

FORM get_data_eh_sect  CHANGING PT_DATA TYPE gty_tab_data.



ENHANCEMENT-SECTION ZZ_JRE_SELECT_ENAHNCE_SEL1 SPOTS ZZ_JRE_SELECT_ENAHNCE_SEL .

select

 matnr,

 ernam,

 ersda

 from mara into CORRESPONDING FIELDS OF table @pt_data UP TO 500 ROWS

  where matnr in @so_matnr

  .

END-ENHANCEMENT-SECTION.

ENDFORM.

Valid choice, but it gives more freedom/options then I wanted to give (the whole select can be replaced/altered, not just fields added) . I agree that this can be view an advantage as well.

 

Build the field list dynamically and provide an enhancement point to add more fields to it;

FORM get_data_dynamic_list_enhp  CHANGING PT_DATA TYPE gty_tab_data.



data lt_fields type table of string.

lt_fields = value #(

( ` MATNR  ,`)

( ` ERNAM  ,`)

( ` ERSDA   `)

).



*ENHACEMENT-Point HERE;

ENHANCEMENT-POINT ZZ_JRE_SELECT_ENAHNCE_SEL2 SPOTS ZZ_JRE_SELECT_ENAHNCE_SEL .



*ADD:

* ,

* [yourFild_1],

*....

*[yourfild_D]



select

 (lt_fields)

 from mara into CORRESPONDING FIELDS OF table @pt_data UP TO 500 ROWS

  where matnr in @so_matnr

  .

ENDFORM.

Valid, too; you could not only add to but also remove from the fields list..
But: we lose all static checks, which I think is a big drawback.
(e.g. misspelling a fieldname will not give a syntax-error (which would be easy to find and solve) but cause trouble at runtime. )

 

My solution:

 

Move the field list to a CDS View and select * from it:

@AbapCatalog.sqlViewName: 'ZZ_MARA1'

@AbapCatalog.compiler.compareFilter : true

@AccessControl.authorizationCheck: #NOT_REQUIRED

@EndUserText.label: 'Select from MARA for Demo'

define view zz_jre_sel_mara as select from mara {

    matnr,

    ernam,

    ersda

}

 

FORM get_data_from_cds  CHANGING PT_DATA TYPE gty_tab_data.



select

 *

 from zz_jre_sel_mara into CORRESPONDING FIELDS OF table @pt_data UP TO 500 ROWS

  where matnr in @so_matnr

  .

ENDFORM.

 

The CDS-view can be extended with a - well - extend view:

@AbapCatalog.sqlViewAppendName: 'ZZ_MARA11'

@EndUserText.label: 'Extending zz_jre_sel_mara 1'

extend view zz_jre_sel_mara with zz_jre_sel_mara_ext1 {

    mara.meins

// mara.[yy_yourfield_1]

// mara.[yy_yourfield_2]    

}

 

 

And this it to show it actually works:



-> Indeed, MARA-MEINS is selected together with the other fields!



Ho do you tackle this problem? Do you (have to) care about your field lists being extendable?

best
Joachim