Object reference error

Object reference error

Post by Mark A. Se » Thu, 14 Oct 2004 22:17:12


I am working on a travel site application that illustrates inheritance and
polymorphism. The abstract base class is Reservable. The three derived
classes are Hotel, Car, and Flight.

I have the following method, which acts as a controller class between the
form and the above classes. The method's purpose is to accept a Hotel, Car,
or Flight object and add it to theReservations ArrayList:
Public Class ReservableController
Private theReservations As System.Collections.ArrayList

Public Sub addReservation(ByRef aReservation As Reservable)
theReservations.Add(aReservation)
End Sub

...
End Class

I receive an object reference error when it attempts to run the Add method.
aReservation is not Nothing when it hits the method. Any ideas?

Mark Serva
The University of Delaware
 
 
 

Object reference error

Post by Jay B. Har » Thu, 14 Oct 2004 22:40:48

Mark,
Does ReservableController have a constructor?

Do you ever initialize the theReservations variable?

Hope this helps
Jay

 
 
 

Object reference error

Post by Mark A. Se » Thu, 14 Oct 2004 22:54:32

Never mind. I found the problem.

Mark