ABAP OO - Class cl_bcs

Question

Hi,
I'm quite new to abap oo but...anyway:
I get a exception when I try to call
call method lo_bcs->set_sender
1. Any pointers to why this code doesn't work.
2. Why can't I do a CREATE OBJECT on lo_bcs.
method SETADDRESS_TO_FROM .
data: lo_sender type ref to if_sender_bcs.
data: lo_bcs  type ref to cl_bcs.
*CREATE OBJECT lo_bcs. DONT WORK!!!?
try.
      lo_sender = cl_cam_address_bcs=>create_internet_address( i_address_string = '[email protected]' ).
catch cx_address_bcs.
      exit.
endtry.
  TRY.
  call method lo_bcs->set_sender
    exporting
      i_sender        = lo_sender.
   CATCH CX_SEND_REQ_BCS .
  ENDTRY.
endmethod.
//Martin

Answer 1

Hello Martin,
If the Instantiation for the class is defined to be <i>Private</i>, then you
cannot create the object of the class outside of the class.
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You have asked: <i>Is this a common approach in the abap oo world ? </i>.
There's nothing common or uncommon about it. It depends on what functionality
needs to be achieved.
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<i>Looks strange....why do they do this?</i>
In Java, you can actually make the constructor as private. In ABAP, however,
that is not possible. So this is another way of achieving equivalent
functonality.
=============================================================================
Now you'd like to know <i>Why do they do this...?</i>
That is a reasonably big discussion and cannot possible be explained satisfactorily
in a Forum Post. but I can tell you something: This way of disallowing external
instantiation for a class is the key to implementing OO Design Patterns.
As I had said, you can easily find other weblogs and Forum posts which can introduce
you to what these are.
Regards,
Anand Mandalika.