Error when calling a method inside a form routine...

Question

Hello experts,
I am trying to call a method inside a form but it is giving me an error. The error is:
Access not possible using 'NULL' object reference.
Anyway, below is my code guys:
START-OF-SELECTION.
  DATA: main          TYPE REF TO lcl_main,
        old_and_new   TYPE REF TO lcl_old_and_new,
        check_changes TYPE REF TO lcl_check_changes,
        messages      TYPE REF TO lcl_messages.
  CREATE OBJECT: main, old_and_new, check_changes, messages.
      FORM get_orig_contents_of_zts0001                             *
FORM get_orig_contents_of_zts0001.
  CALL METHOD main->export_old_recs.
ENDFORM.
Help would be greatly appreciated. Thanks a lot and take care!

Answer 1

Before the "START-OF-SELECTION " just add this sentense :
<b>class lcl_main definition deferred.</b>
CLASS Definition.
ENDCLASS.
CLASS Implementation.
ENDCLASS.
START-OF-SELECTION.
*Do your coding here
<b>in this way we are deferring the class definition for later</b>