Thread: Pure Virtual Polymorphism HELP

Originally Posted by Bubba

Eh?

I still don't understand why you need the GetClass().

You're right - s/he wouldn't. All objects of a derived class can be treated by default as if they are instances of a base class (not withstanding a couple of techniques that can be used to prevent that, but they're not relevant here).

Originally Posted by Syndacate

Really? I'm not sure they'd have code like that in a 'basic c++ programming' book, and yeah, I've really never seen code like that...but I don't really think I need to 'go back to basics' to find it. It's some weird crap that people in the industry experience that I've been exposed to don't do, so I've never had to worry about it, if I did, I'd probably ask somebody there, or here, or somewhere.

It looks like it just means that the sub class inherits from that 'instance' - but assuming it doesn't, not sure what it means or how it differs from 'normal' inheritance. Besides, it looks like it becomes a pain with long inheritance chains (ie. GUI frameworks), especially with multiple inheritance.

There is nothing weird with that code, and yes it is basics.
That example was really moot since it calls the default constructor on x, but that is done implicitly anyway. But if classA had a non-default constructor that took one or more parameters, then you would have to initialize the object by calling its constructor via the initializer list.