virtual function question

[vkaul1]

I had a question about base classes that have virtual functions. If we have base class shape and then there is a derive class object rectangle with additional member length.
And we define
shape *s= new rectangle;
int length= s->length;
Will this work if length is an integer and public member of derived class rectangle and shape is pure abstract class?

[Nikitozz]

No. It won't. The Sahpe class doesn't know anything about the length member.

[Ajay Vijay]

The concept is virtual function, and not virtual member. You cannot have data-member as virtual.
Also, the function must be defined in base class as virtual.