Getting error for null object reference, while implementing class in module pool ?

[nbitish]

Hello everyone,

Please help me eliminate this error, I am new to abap. Would be very thankful for that.

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class ZCL_NB_CLASS definition
public
create public .

public section.
*"* public components of class ZCL_NB_CLASS
*"* do not include other source files here!!!

methods DEPOSIT
importing
value(AMOUNT) type DMBTR
returning
value(NEW_BALANCE) type DMBTR .
methods SET_BALANCE
importing
value(AMOUNT) type DMBTR
returning
value(NEW_BALANCE) type DMBTR .
methods WITHDRAW
importing
value(AMOUNT) type DMBTR
returning
value(NEW_BALANCE) type DMBTR
exceptions
INSUFFICIENT_FUNDS .
methods MESSAGE
exporting
!MESS type BAPIRET2 .
protected section.
*"* protected components of class ZCL_NB_CLASS
*"* do not include other source files here!!!
private section.
*"* private components of class ZCL_NB_CLASS
*"* do not include other source files here!!!

class-data BALANCE type DMBTR .
ENDCLASS.



CLASS ZCL_NB_CLASS IMPLEMENTATION.


* <SIGNATURE>---------------------------------------------------------------------------------------+
* | Instance Public Method ZCL_NB_CLASS->DEPOSIT
* +-------------------------------------------------------------------------------------------------+
* | [--->] AMOUNT TYPE DMBTR
* | [<-()] NEW_BALANCE TYPE DMBTR
* +--------------------------------------------------------------------------------------</SIGNATURE>
method DEPOSIT.

BALANCE = balance + AMOUNT.
new_balance = balance.

endmethod.


* <SIGNATURE>---------------------------------------------------------------------------------------+
* | Instance Public Method ZCL_NB_CLASS->MESSAGE
* +-------------------------------------------------------------------------------------------------+
* | [<---] MESS TYPE BAPIRET2
* +--------------------------------------------------------------------------------------</SIGNATURE>
method MESSAGE.

MESS-message = 'Message has been called'.
MESS-type = 'S'.

endmethod.


* <SIGNATURE>---------------------------------------------------------------------------------------+
* | Instance Public Method ZCL_NB_CLASS->SET_BALANCE
* +-------------------------------------------------------------------------------------------------+
* | [--->] AMOUNT TYPE DMBTR
* | [<-()] NEW_BALANCE TYPE DMBTR
* +--------------------------------------------------------------------------------------</SIGNATURE>
method SET_BALANCE.

balance = new_balance.

endmethod.


* <SIGNATURE>---------------------------------------------------------------------------------------+
* | Instance Public Method ZCL_NB_CLASS->WITHDRAW
* +-------------------------------------------------------------------------------------------------+
* | [--->] AMOUNT TYPE DMBTR
* | [<-()] NEW_BALANCE TYPE DMBTR
* | [EXC!] INSUFFICIENT_FUNDS
* +--------------------------------------------------------------------------------------</SIGNATURE>
method WITHDRAW.

IF balance GE AMOUNT.
balance = balance - AMOUNT.
NEW_BALANCE = BALANCE.
ELSE.
RAISE INSUFFICIENT_FUNDS.
ENDIF.
endmethod.
ENDCLASS.

[geert-janklaps]

Hi,

Did you instantiate your object in the module pool before calling a method of the class?

"Classic notation":
DATA: lo_nb_class TYPE REF TO zcl_nb_class.
CREATE OBJECT lo_nb_class.
lo_nb_class->withdraw( 500 ).

"New short syntax":
DATA(lo_nb_class) = NEW zcl_nb_class( ).
lo_nb_class->withdraw( 500 ).

[nbitish]

Dear Greet,
Thanks for reply, I am using the below code for that, Also I have already created the object.

**************************************Init**********************************
  DATA OBJ TYPE REF TO ZCL_NB_CLASS.
  DATA TRANS_BALANCE TYPE DMBTR.
  DATA WITHDRAW TYPE DMBTR.
  DATA BALANCE_LEFT TYPE DMBTR.

START-OF-SELECTION.
  CREATE OBJECT OBJ .
DATA LV_MESSAGE TYPE BAPIRET2.

***********************************Init**************************************

***********************************PAI******************************************
CASE SY-UCOMM.
  WHEN 'DRAW'.
  CALL METHOD  OBJ->deposit( EXPORTING AMOUNT = TRANS_BALANCE

                                  RECEIVING  NEW_BALANCE = BALANCE_LEFT ).
  WHEN 'SET'.
  CALL METHOD  OBJ->set_balance( EXPORTING AMOUNT = TRANS_BALANCE
                                  RECEIVING  NEW_BALANCE = BALANCE_LEFT ).

  WHEN 'DEPO'.
  CALL METHOD  OBJ->withdraw( EXPORTING AMOUNT = TRANS_BALANCE

                                  RECEIVING  NEW_BALANCE = BALANCE_LEFT ).
  WHEN 'MESS'.
  CALL METHOD  OBJ->MESSAGE( IMPORTING MESS = LV_MESSAGE ).

ENDCASE.

************************************PAI***************************************

[nbitish]

This is the error analysis that I am getting...

An exception occurred that is explained in detail below. The exception, which is assigned to class 'CX_SY_REF_IS_INITIAL', was not caught and therefore caused a runtime error. The reason for the exception is: You attempted to use a 'NULL' object reference (points to 'nothing') access a component (variable: "OBJ"). An object reference must point to an object (an instance of a class) before it can be used to access components. Either the reference was never set or it was set to 'NULL' using the CLEAR statement.

But I have already created the object above.

[matt]

Use the code button in the editor to provide your code in a nicely formatted and readable way, and then I might take the time to help you.

[nbitish]

Hi Greet,

My issue is solved. When I created the object in PAI include then it is working fine. But when I am defining it in program it is telling null object

reference. Does it mean that when I am defining it in the PROGRAM the object is not created for the whole " That is not for the includes " ?

[matt]

Runtime knows nothing about includes.

Main program:

... some code ...
INCLUDE sub_program.

With include sub_program

...some more code...

Is EXACTLY the same as

... some code ...
... some more code ...

Includes are just ways of organising source code. That's it. Nothing else.

[nbitish]

Thanks Mathew,

So could you please tell me at which point should I declare my object then.

PROGRAM  ZNB_CLASS_MOD_POO_IMP.
DATA LV_MESSAGE TYPE BAPIRET2.
DATA OBJ TYPEREFTO ZCL_NB_CLASS.
DATA TRANS_BALANCE TYPE DMBTR.
DATA BAL TYPE DMBTR.
DATA BALANCE_LEFT TYPE DMBTR.
*************************** If I declare the object here then I gets error*************************

INCLUDE ZNB_CLASS_MOD_POO_IMP_STATUO01.
INCLUDE ZNB_CLASS_MOD_PAI.                          " I have declared my object in here, then its' working fine.

Regards.

[Sandra_Rossi]

Probably he wouldn't, because Matthew told you he would help you after you improve the formatting of the code in your initial question. If I had the same question as yours, I would first look at your post and then ran away because it's simply unreadable.

[DoanManhQuynh]

idk what is your whole code but i tried with what you gave here, it run as normal where ever i create object. if you declared it before the include, it will become a global variable which available in your whole program. maybe you should re-organize your code first. beside, you are using sy-ucomm here which you should use okcode instead, FYI.