How to call methods at selection screen?

Question

Hi all,
I am developing a program in object oriented abap.
i have defined a class and implementated, and we have to instantiate the class in start of selection.
now the problem is how to call a method at selection screen event.
i want to validate the inputs entered by users. so can i create a static method which can be called without instantiating a class?
please guide me
thanks

Answer 1

Hello Mr A,
Define the method as a Static Method and that will solve your problem. Static methods can be called directly and does not need the class to be instantiated before it can be called.
Data: my_class type ref to zcl_report_utilities.
At Selection-Screen.
Call Method zcl_report_utilities=>check_selections
       exporting
          iv_repnm    = sy-cprog
        importing
          et_messages = lt_msgs.
Start-Of-Selection.
  Create Object my_class
         exporting
            im_pernr  = ls_e1plogi-objid
            im_begda = c_lowdate
            im_endda = c_hidate.
   Call Method my_class->read_infotypes
          exporting
             im_infty = c_org_assn
          changing
             et_infty  = it_infty.
Here you can see how the method check_selections is called before the class zcl_report_utilities is instantiated. The best part about the Static Methods is if you are writing the class in the Class Library (SE24), any other programs can call them directly (if they need to) without needing to instantiating the entire class before the call.
Also note the difference in syntax when calling the static method check_selections to when calling the Instance method read_infotypes.
Hope this solves your issue and please do not forget to reward points.
Cheers,
Sougata.
p.s. if you are defining your class locally (program specific) then use Class-Methods to define a static method.
Edited by: Sougata Chatterjee on May 1, 2008 9:53 AM