Re: polymorphism

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Fri, 12 Jun 2009 12:19:25 +0200

Message-ID:

<h0ta3k$753$1@news.eternal-september.org>

* Anees:

I am using visual studio 2008. Can anyone help, why does the following
polymorphism not working? It is keep giving "base" as output :(

#include <iostream>

using namespace std;

class base {
public:
    base() {
        print();
    }

This will always call base::print, no matter whether print is virtual, because
while executing the base constructor the type of the object is base.

There is a FAQ item that discusses this.

It's nearly always a good idea to read the FAQ.

protected:
    virtual void print() {
        cout << "base" << endl;
    }

};

class derived:public base {
protected:
    virtual void print() {
        cout << "derived" << endl;
    }
};

int _tmain(int argc, _TCHAR* argv[]){
    derived d;

This is a non-standard Microsoft monstrosity.

Why write more in order to make the code non-standard?

In standard C++ write just

int main()

See, it's much less to write.

And it's standard.

}

Cheers & hth.,

- Alf

--
Due to hosting requirements I need visits to <url: http://alfps.izfree.com/>.
No ads, and there is some C++ stuff! :-) Just going there is good. Linking
to it is even better! Thanks in advance!