Article #15449: CONSTRUCTOR CALL TO ANCESTOR WITH VIRTUALS

 Technical Notes Database

TN449D.txt   CONSTRUCTOR CALL TO ANCESTOR WITH VIRTUALS
Category   :Pascal
Platform    :All
Product    :Turbo Pascal  5.5

Description:
Q. If a descendant of a virtual object defines no virtual
   methods of its own, does it need to call the ancestor's
   constructor?
A. If an object is a descendant of a virtual object, it must call
   that ancestor's constructor or it's own constructor. Even if
   the new object does not define any virtuals of its own. For
   example:

     Type
       A = Object
             Constructor Init;
             Procedure AA; Virtual;
       End;
       B = Object ( A )
       End;

   For each instance of A and of B, Init must be called or the
   Virtual Method Table pointer will not be loaded correctly.


Reference:


7/16/98 4:35:32 PM
 

Last Modified: 01-SEP-99