OOP Question about common method in base class (probably simple)

[GregFreeman]

My OOP naivety shows again, but oh well, I'll learn, albeit slowly. I have a "network connection" base class and from it I have some child classes. I want to create a public method to check if a connection is valid. It seems like this is a method that should somehow go in the base class because it will be the same for all classes (check a connection refnum whether it's tcp,udp, etc, and see if it's valid). But, I am not sure how to best accomplish getting the connection refnum which is held in the child class, into the base class. I obviously don't want some sort of public accessor to call to return the refnum to be passed to the base classes method because I don't want the connection refnum available outside the class. But, I was trying to avoid having a "is connection valid" method in every single class also, when it seems a generic method would work fine.

Suggestions?

Edited July 28, 2012 by for(imstuck)

[drjdpowell]

Other than for TCP and UDP, how many different “Is Valid” methods can you possibly need?

Note that you can make a method “protected”, which would allow your base class to call child-class methods without making the methods public.

Also note this conversation and consider if you really need an “Is Valid” method.

[Aristos Queue]

Add a dynamic dispatch protected scope "Get Refnum" to the base class. Make it "Must Override". Call it in the Is Valid implementation.

[Jeffrey Habets]

I'd expect you need to do more then just a simple valid-refnum check to see if a connection is valid and that it would be different actions depending on the protocol that is used. So I would opt for implementing a dynamic dispatch "CheckConnection" method and make it "Must Override" so that each child has to implements it's own.

If you're really certain that you can use the same piece of code to check connection for all child implementations, I vote for AQ's solution above.

[crelf]

It sounds like your refnum is the same type between each of the child classes? If so, why not put it in the parent class?

[Aristos Queue]

It sounds like your refnum is the same type between each of the child classes?

His refnum is explicitly not the same. It's TCP or UDP or whatever.

I should note, regarding my solution, that each child class would have to cast its reference as an int32 in order to return it to parent.

Jeffery raises the point about doing more than just checking for Not A Refnum... i.e., checking if a non-zero refnum is still valid. Very important, for (imstuck): read this please:

http://lavag.org/top...ur-app-at-risk/