• Advertisement

Archived

This topic is now archived and is closed to further replies.

Member function pointers

This topic is 4995 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Is it possible to call a virtual member function of a base class, that has been overriden in a derived class, from a base class function pointer.
struct base
{
	virtual void func(){
		std::cout << "base";
	}
};

struct derived : base
{
	void func(){
		std::cout << "derived";
	}
};
	
int main(){  
	void (base::*pfun)() = &base::func;
	base* pbase = new derived;
	(pbase->*pfun)();
}
I was expecting this to call the base class member function, but it seems the virtual function mechanism works on member function pointers too. Is there a way to call the base class function, without making it unvirtual.

Share this post


Link to post
Share on other sites
Advertisement
I just tried the following and it actually works:
int main(void)
{
base *b;
derived d;

b = &d;

b->foo(); // Prints "derived" as expected


b->base::foo(); // Prints "base"


return 0;
}


Note that the :: operator has the highest precedence, so it is evaluated before the arrow, dot, and parentheses operators, so the above code is equivalent to b->(base::foo)().

Share this post


Link to post
Share on other sites
quote:
Original post by quant
Is there a way to call the base class function, without making it unvirtual.

Nope, this is actually a semi-gripe I have with the language, though only semi-gripe because it should rarely logically make sense for you to do such a thing. It would be nice if you could choose between dynamic binding and static binding of member function pointers, possibly by having a non-virtual member function pointer type (convertable to the standard member function pointer type) which would be more similar to a regular function pointer in addition to also having the standard member function pointer type we have now.
Instead, your only solution is to make a separate non-virtual function which is called by the virtual function, and then make the poitner point to the nonvirtual function.

[edited by - Polymorphic OOP on May 19, 2004 12:03:55 PM]

Share this post


Link to post
Share on other sites

  • Advertisement