Re: virtual function in inherited class not getting called

From:
Barry <dhb2000@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 10 Apr 2008 17:31:35 +0800
Message-ID:
<ftksii$p75$1@news.cn99.com>
Angus wrote:

I have a base class CEventSelect a bit like this:

class CEventSelect
{
 virtual void OnConnected();
}

and a network interface class a bit like this:

class networkinterface : public CEventSelect
{
    virtual void OnConnected();
}

The base CEventSelect class calls it's OnConnected() function when a
client receives notification from the network that it is connected.
But I wanted my networkinterface::OnConnected() method to be called?
But it wasn't. I understand polymorphic functions and I think I
understand why it is not working the way I wanted. Because
CEventSelect calls its own OnConnected() method does mean that the
inheriting OnConnected() will be called. But this is the behaviour I
want.

The actual connection is notified by the base class - but I want my
interface class to someone get notified of the connection.

How can I get the networkinterface class to be notified about the
connection?


I don't know how your code was written,
But I guess the following code may help.

#include <iostream>

class CEventSelect
{
public:
     virtual void OnConnected() { std::cout << "CEventSelect" <<
std::endl; }
};

class networkinterface : public CEventSelect
{
public:
     virtual void OnConnected() { std::cout << "networkinterface" <<
std::endl; }
};

void call1(CEventSelect event)
{
     event.OnConnected();
}

void call2(CEventSelect& event)
{
     event.OnConnected();
}

void call3(CEventSelect* event)
{
     event->OnConnected();
}

int main()
{
     networkinterface ni;
     call1(ni); // by value
     call2(ni); // by reference
     call3(&ni);// by address
}

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