Observer Pattern - Events containing different data

[Christopher]

The observer pattern itself is easy enough. I've implemented it using
a Event that contains data for any Event type I forsee my application
using. My problem is I don't want one and only one general purpose
type of Event. I want to write my design in such a way that more Event
Types can be created and used down the road as needed. How can you
design the Events in such a way that more can be handled later by the
same Observer and Subject classes when they don't know what your
Events look like right now?

 

[Victor Bazarov]

The observer pattern itself is easy enough. I've implemented it using
a Event that contains data for any Event type I forsee my application
using. My problem is I don't want one and only one general purpose
type of Event. I want to write my design in such a way that more Event
Types can be created and used down the road as needed. How can you
design the Events in such a way that more can be handled later by the
same Observer and Subject classes when they don't know what your
Events look like right now?

I am not sure this is a C++ question. Try 'comp.object' as well.

I would probably try to design a polymorphic pair Observer/Event. You
cannot make the same observer observe any type of event, but you can
make more [different] observers to observe the events they know about.
Also, in such case you can make Events aware of the Observers that can
observe them...

V