Display ALV Using Factory Pattern in SAP

Factory Pattern 


When you work with ABAP Objects you always need to create instances of classes. Even if you use "CREATE OBJECT" to create those instances, you probably faced with the problem, that it is not so comfortable as if you have a function for creating objects in the same way. Or, you have a complex logic to create each instance.
For those cases, there is a design-pattern for creating instances. This pattern is called "Factory"-pattern. There is also a pattern called "factory-method", which is different, because it combines the creation and relationship of objects

The factory-pattern is one of the most used design pattern. It creates object instances without exposing the concrete instantiation logic. The instantiated objects will be accessible through an interface, which encapsulate the concrete implementation to the users.

*&---------------------------------------------------------------------*
*& This code snippet will show how to use the CL_SALV_TABLE to
*&   generate the ALV
*&---------------------------------------------------------------------*
REPORT  ztest_oo_alv_main.
*
*----------------------------------------------------------------------*
*       CLASS lcl_report DEFINITION
*----------------------------------------------------------------------*
CLASS lcl_report DEFINITION.
*
  PUBLIC SECTION.
*
*   Final output table
    TYPES: BEGIN OF ty_vbak,
           vbeln TYPE vbak-vbeln,
           erdat TYPE erdat,
           auart TYPE auart,
           kunnr TYPE kunnr,
           END   OF ty_vbak.
*
    DATA: t_vbak TYPE STANDARD TABLE OF ty_vbak.
*
*   ALV reference
    DATA: o_alv TYPE REF TO cl_salv_table.
*
    METHODS:
*     data selection
      get_data,
*
*     Generating output
      generate_output.
*
*$*$*.....CODE_ADD_1 - Begin..................................1..*$*$*
*
*    In this section we will define the private methods which can
*      be implemented to set the properties of the ALV and can be
*      called in the
*
*$*$*.....CODE_ADD_1 - End....................................1..*$*$*
*
ENDCLASS.                    "lcl_report DEFINITION
*
*
START-OF-SELECTION.
  DATA: lo_report TYPE REF TO lcl_report.
*
  CREATE OBJECT lo_report.
*
  lo_report->get_data( ).
*
  lo_report->generate_output( ).
*
*----------------------------------------------------------------------*
*       CLASS lcl_report IMPLEMENTATION
*----------------------------------------------------------------------*
CLASS lcl_report IMPLEMENTATION.
*
  METHOD get_data.
*   data selection
    SELECT vbeln erdat auart kunnr
           INTO  TABLE t_vbak
           FROM  vbak
           UP TO 20 ROWS.
*
  ENDMETHOD.                    "get_data
*
*.......................................................................
  METHOD generate_output.
* New ALV instance
*   We are calling the static Factory method which will give back
*   the ALV object reference.
*
* exception class
    DATA: lx_msg TYPE REF TO cx_salv_msg.
    TRY.
        cl_salv_table=>factory(
          IMPORTING
            r_salv_table = o_alv
          CHANGING
            t_table      = t_vbak ).
      CATCH cx_salv_msg INTO lx_msg.
    ENDTRY.
*
*$*$*.....CODE_ADD_2 - Begin..................................2..*$*$*
*
*    In this area we will call the methods which will set the
*      different properties to the ALV
*
*$*$*.....CODE_ADD_2 - End....................................2..*$*$*
*
*
* Displaying the ALV
*   Here we will call the DISPLAY method to get the output on the screen
    o_alv->display( ).
*
  ENDMETHOD.                    "generate_output
*
*$*$*.....CODE_ADD_3 - Begin..................................3..*$*$*
*
*    In this area we will implement the methods which are defined in
*      the class definition
*
*$*$*.....CODE_ADD_3 - End....................................3..*$*$*
*
*
ENDCLASS.                    "lcl_report IMPLEMENTATION