ALV OO de FONDO

[oskymoreok]

Disculpa que te moleste nuevamente pero me da un DUMP

Err.tmpo.ejec. OBJECTS_OBJREF_NOT_ASSIGNED
Excep. CX_SY_REF_IS_INITIAL
Fecha y hora 25.03.2015 15:08:09



An exception occurred that is explained in detail below.
The exception, which is assigned to class 'CX_SY_REF_IS_INITIAL', was not
caught in
procedure "ALV" "(FORM)", nor was it propagated by a RAISING clause.
Since the caller of the procedure could not have anticipated that the
exception would occur, the current program is terminated.
The reason for the exception is:
You attempted to use a 'NULL' object reference (points to 'nothing')
access a component (variable: "GR_COLUMNS").
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.


y el error en el codigo es

>>>>> gr_column ?= gr_columns->get_column( 'DATUM_BAL' ).

de paso te pregunto que es el '?='

te comento yo entendi, segun el errror que gr_columns es una variables que estoy tratando de meter en una referencia null de gr_column, estoy en lo cierto? que deberia hacer?