topic Re: ABAP Objects - MVC in Application Development and Automation Discussions

ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 01:57:21 GMT

Hello all,

I am trying to a tutorial from a website which were published by Mr Naimesh Patel.

It is a tutorial showing an example of MVC of ABAP Objects.

You can find the URL http://help-abap.blogspot.com/2008/10/abap-objects-design-patterns-model-view_13.html.

I have tried to copy the necessary code including methods and parameters as provided in the article. However while compiling, I got an error Field "O_MODEL->GET_DATA" is unknown.

Based on the article and code, anyone knows how should I resolve this?

What should I define for o_model?

I cant wait for the author to reply my message as I do not know when he will be asnwering me question.

Thanks in advance.

Re: ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 02:41:35 GMT

Have you declared any attribute with O_model?

This type of error comes when we have not declared any attribute or u might have declared but written incorrectly (spelling) in method.

Re: ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 02:45:37 GMT

Hi Pradeep,

Thanks for your reply. Yes, you are right. I have not declared the o_model, as the article does not mentioned this.

Any idea what should the o_model defines in attribute?

Re: ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 03:12:51 GMT

We can declare it as an object like

DATA : obj TYPE REF TO object.

Re: ABAP Objects - MVC

uwe_schieferstein — Tue, 28 Apr 2009 03:22:44 GMT

Hello Myahsam

The definition of O_MODEL as root class OBJECT obviously does not work because this class does not have any methods.

However, it is clear what O_MODEL should be because the Controller class is a composition containing a reference to the model class as well as the view class. Thus:


" O_... = Object instance attribure
" ..._MODEL = representing the model in MVC

DATA: o_model    TYPE REF TO zcl_model.

Well, that's what Naimesh says in this tutorial:

>Our controller class ZCL_CONTROL will have a method GET_OBJECT which will give us an object of the >model class. We require a public attribute which can refer to the object created in the method >GET_OBJECT.

>Controller Method definition:

Regards

Uwe

Re: ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 03:26:35 GMT

yes its correct the type should be class_name.

Re: ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 04:08:13 GMT

Hi all,

After added in the o_model TYPE REF TO zcl_test_model.. I am still having the same error message "Field "O_MODEL->GET_DATA" is unknown.".


*&---------------------------------------------------------------------*
*& Report  ZTEST_OOP_MVC_ALV
*&---------------------------------------------------------------------*

REPORT  ZTEST_OOP_MVC_ALV.
*
START-OF-SELECTION.
*---------
* Controller
*---------
DATA: lo_control TYPE REF TO zcl_test_control,
      o_model   TYPE REF TO zcl_test_model.
*
* Initiate controller
CREATE OBJECT lo_control.
*
* Get the object from Control
CALL METHOD lo_control->get_object
  EXPORTING
    if_name = 'ZCL_TEST_MODEL'.
*
*---------
* Model - Business Logic
*---------
* Date Range
DATA: r_erdat  TYPE RANGE OF vbak-erdat,
      la_erdat LIKE LINE OF r_erdat.
*
la_erdat-sign = 'I'.
la_erdat-option = 'BT'.
la_erdat-low = sy-datum - 10.
la_erdat-high = sy-datum.
APPEND la_erdat TO r_erdat.
*
* Get data method
CALL METHOD lo_control->o_model->get_data
  EXPORTING      ir_erdat = r_erdat.
*
*---------
* View - ALV output
*---------
DATA: lo_alv TYPE REF TO cl_salv_table,
      lx_msg TYPE REF TO cx_salv_msg.

TRY.
  cl_salv_table=>factory(
  IMPORTING
    r_salv_table = lo_alv
  CHANGING
    t_table      = lo_control->o_model->t_vbak ).
  CATCH cx_salv_msg INTO lx_msg.
ENDTRY.
*
*Displaying the ALV
lo_alv->display( ).

Re: ABAP Objects - MVC

Former Member — Tue, 28 Apr 2009 07:32:19 GMT

After shifted the o_model TYPE REF TO zcl_test_model to zcl_test_control attribute. The program compiled successfully.

Thanks to all.