How to approach ABAP OO programming the right way...

Question

Hello experts,
I am an old school procedural ABAP programmer and I recently I have been experementing with ABAP Objects since I've read a few columns the advantages of ABAP OO and also currently learning its syntax. Now, does ABAP Objects conform to the old way of say, doing reports like at selection-screen output, at selection-screen, on value-request for..., start-of-selection, end-of-selection, top-of-page, etc. I have been doing some practice programs and I am not sure if my approach is correct. Example, I created a class named cl1 and I have a method named upload. Now, the UPLOAD method contains the function 'GUI_UPLOAD'. Is this the right way of doing it? Also, How come I cannot create structures inside a class?
Again, thanks guys and have a nice day!

Answer 1

Hi,
I have these three progs from one of the previous posts.
Good approach on using constructors. I am not finding the original link.
*& Report ZABAP_OBJ_01 *
REPORT zabap_obj_01 .
PARAMETERS : p_vbeln LIKE vbap-vbeln OBLIGATORY,
             p_matnr LIKE mara-matnr.
TYPES : BEGIN OF ty_vbap,
vbeln TYPE vbap-vbeln,
matnr TYPE vbap-matnr,
arktx TYPE vbap-arktx,
END OF ty_vbap.
* CLASS sales_order DEFINITION
CLASS sales_order DEFINITION.
  PUBLIC SECTION.
    DATA : v_matnr TYPE mara-matnr,
    v_vbeln TYPE vbap-vbeln.
    METHODS : constructor IMPORTING vbeln TYPE vbap-vbeln
    matnr TYPE mara-matnr OPTIONAL.
    DATA : it_vbap TYPE STANDARD TABLE OF ty_vbap.
    METHODS : get_vbap_details,
    disp_vbap_details.
ENDCLASS. "sales_order DEFINITION
* CLASS sales_order IMPLEMENTATION
CLASS sales_order IMPLEMENTATION.
  METHOD get_vbap_details.
    CLEAR : it_vbap.
    REFRESH : it_vbap.
    SELECT vbeln
    matnr
    arktx
    FROM vbap
    INTO TABLE it_vbap
    WHERE vbeln = p_vbeln.
  ENDMETHOD. "get_vbap_details
  METHOD constructor.
    CLEAR : v_vbeln,
    v_matnr.
    v_vbeln = vbeln.
    v_matnr = matnr.
  ENDMETHOD. "constructor
  METHOD disp_vbap_details.
    DATA : wx_vbap LIKE LINE OF it_vbap.
    LOOP AT it_vbap INTO wx_vbap.
      WRITE :/ wx_vbap-vbeln,
      wx_vbap-matnr,
      wx_vbap-arktx.
    ENDLOOP.
    CLEAR : it_vbap.
  ENDMETHOD. "disp_vbap_details
ENDCLASS. "sales_order IMPLEMENTATION
DATA : obj TYPE REF TO sales_order.
START-OF-SELECTION.
  IF NOT p_matnr IS INITIAL.
    CREATE OBJECT obj EXPORTING vbeln = p_vbeln
    matnr = p_matnr.
  ELSE.
    CREATE OBJECT obj EXPORTING vbeln = p_vbeln.
  ENDIF.
  CALL METHOD obj->get_vbap_details.
  CALL METHOD obj->disp_vbap_details.
*& report ziga_abapobjects_asgn01 *
  REPORT ziga_abapobjects_asgn01 .
  PARAMETER : p_matnr LIKE mara-matnr.
* CLASS lcl_material DEFINITION
CLASS lcl_material DEFINITION.
  PUBLIC SECTION.
    DATA: v_matnr TYPE mara-matnr.
    METHODS : constructor IMPORTING matnr TYPE mara-matnr,
    get_material_description.
  PRIVATE SECTION.
    DATA : v_maktx TYPE makt-maktx.
ENDCLASS. "lcl_material DEFINITION
* CLASS lcl_material IMPLEMENTATION
CLASS lcl_material IMPLEMENTATION.
  METHOD get_material_description.
    CLEAR v_maktx.
    SELECT SINGLE maktx INTO v_maktx
    FROM makt
    WHERE matnr = v_matnr AND
    spras = 'E'.
  ENDMETHOD. "get_material_description
  METHOD constructor.
    CLEAR v_matnr.
    v_matnr = matnr.
  ENDMETHOD. "constructor
ENDCLASS. "lcl_material IMPLEMENTATION
DATA : obj TYPE REF TO lcl_material.
START-OF-SELECTION.
  CREATE OBJECT obj EXPORTING matnr = p_matnr.
  CALL METHOD obj->get_material_description.
  prg3)
  report ziga_abapobjects_asgn01 .
  PARAMETER : p_matnr LIKE mara-matnr.
* CLASS lcl_material DEFINITION
CLASS lcl_material DEFINITION.
  PUBLIC SECTION.
    METHODS : constructor IMPORTING matnr TYPE mara-matnr,
    write_material_desc.
    CLASS-METHODS : class_constructor.
  PRIVATE SECTION.
    CLASS-DATA: v_matnr TYPE mara-matnr.
    DATA : v_maktx TYPE makt-maktx.
    METHODS : get_material_description.
ENDCLASS. "lcl_material DEFINITION
* CLASS lcl_material IMPLEMENTATION
CLASS lcl_material IMPLEMENTATION.
  METHOD get_material_description.
    CLEAR v_maktx.
    SELECT SINGLE maktx INTO v_maktx
    FROM makt
    WHERE matnr = v_matnr AND
    spras = 'E'.
  ENDMETHOD. "get_material_description
  METHOD constructor.
    WRITE :/ 'Inside Instance Constructor'.
    CLEAR v_matnr.
    v_matnr = matnr.
    CALL METHOD get_material_description.
  ENDMETHOD. "constructor
  METHOD write_material_desc.
    WRITE :/ 'Material Description :', v_maktx.
  ENDMETHOD.                    "write_material_desc
  METHOD class_constructor.
    WRITE :/ 'Inside Static Constructor'.
  ENDMETHOD.                    "class_constructor
ENDCLASS. "lcl_material IMPLEMENTATION
DATA : obj TYPE REF TO lcl_material,
obj1 TYPE REF TO lcl_material.
START-OF-SELECTION.
  CREATE OBJECT obj EXPORTING matnr = p_matnr.
  CALL METHOD obj->write_material_desc.
  CREATE OBJECT obj1 EXPORTING matnr = '000000000000000110'.
  CALL METHOD obj1->write_material_desc.
  CALL METHOD obj->write_material_desc.
  prg4)
  report ziga_abapobjects_asgn01 .
  PARAMETER : p_matnr LIKE mara-matnr.
* CLASS lcl_material DEFINITION
CLASS lcl_material DEFINITION.
  PUBLIC SECTION.
    METHODS : constructor IMPORTING matnr TYPE mara-matnr,
    write_material_desc,
    get_material_description.
    CLASS-METHODS : class_constructor.
  PRIVATE SECTION.
    CLASS-DATA: v_matnr TYPE mara-matnr.
    DATA : v_maktx TYPE makt-maktx.
ENDCLASS. "lcl_material DEFINITION
* CLASS lcl_material IMPLEMENTATION
CLASS lcl_material IMPLEMENTATION.
  METHOD get_material_description.
    CLEAR v_maktx.
    SELECT SINGLE maktx INTO v_maktx
    FROM makt
    WHERE matnr = v_matnr AND
    spras = 'E'.
  ENDMETHOD. "get_material_description
  METHOD constructor.
    WRITE :/ 'Inside Instance Constructor'.
    CLEAR v_matnr.
    v_matnr = matnr.
  ENDMETHOD. "constructor
  METHOD write_material_desc.
    WRITE :/ 'Material Description :', v_maktx.
  ENDMETHOD.                    "write_material_desc
  METHOD class_constructor.
    WRITE :/ 'Inside Static Constructor'.
  ENDMETHOD.                    "class_constructor
ENDCLASS. "lcl_material IMPLEMENTATION
DATA : obj TYPE REF TO lcl_material,
obj1 TYPE REF TO lcl_material.
START-OF-SELECTION.
  CREATE OBJECT obj EXPORTING matnr = p_matnr.
  CALL METHOD obj->get_material_description.
  CALL METHOD obj->write_material_desc.
  CREATE OBJECT obj1 EXPORTING matnr = '000000000000000110'.
  CALL METHOD obj1->get_material_description.
  CALL METHOD obj1->write_material_desc.
  CALL METHOD obj->get_material_description.
  CALL METHOD obj->write_material_desc.
  REPORT ziga_abapobjects_asgn01 .
  PARAMETER : p_matnr LIKE mara-matnr.
* CLASS lcl_material DEFINITION
CLASS lcl_material DEFINITION.
  PUBLIC SECTION.
    CLASS-METHODS : write_material_desc,
    get_material_description,
    class_constructor.
  PRIVATE SECTION.
    CLASS-DATA: v_matnr TYPE mara-matnr.
    CLASS-DATA: v_maktx TYPE makt-maktx.
ENDCLASS. "lcl_material DEFINITION
* CLASS lcl_material IMPLEMENTATION
CLASS lcl_material IMPLEMENTATION.
  METHOD get_material_description.
    CLEAR v_maktx.
    SELECT SINGLE maktx INTO v_maktx
    FROM makt
    WHERE matnr = v_matnr AND
    spras = 'E'.
  ENDMETHOD. "get_material_description
  METHOD write_material_desc.
    WRITE :/ 'Material Description :', v_maktx.
  ENDMETHOD.                    "write_material_desc
  METHOD class_constructor.
    WRITE :/ 'Inside Static Constructor'.
    v_matnr = '000000000000000110'.
  ENDMETHOD.                    "class_constructor
ENDCLASS. "lcl_material IMPLEMENTATION
START-OF-SELECTION.
  CALL METHOD lcl_material=>get_material_description.
  CALL METHOD lcl_material=>write_material_desc.
Arun Sambargi.