virtual operator()

Hi there,

I want to pass a Functor interface as a function argument :

Code:

---

class IFoo
{
 public:
  virtual ~IFoo(){}
  virtual bool operator()() const = 0;
}
class Foo : public IFoo
{
 public:
  bool operator()() const;
}

---

Now a small voice tells me that the operator() cannot be virtual, and therefore a function "apply" should be implemented. But when i try it compiles and runs.

Does anyone know issues about this, or should i just ignore that small voice..

Thanks!

Mark

Why shouldn't it be allowed to be virtual?

Operators are like regular functions in the vtable - they just have "strange" names.

--
Mats

Yes yes I know, but I am so convinced I've read something about it..
I know the operator= cannot be inherited , but yeah for the others I didn't see any reason why neither...

Probably a very bad source or a bad interpretation from my side...

Quote:

---

I know the operator= cannot be inherited

---

Yes it can.

Well it can be, but it just doesn't seem to be B's operator=

Code:

---

#include <iostream>

class A
{
public:
    virtual const A& operator = (const A&)
    {
        std::cout << "A=A\n";
        return *this;
    }
};

class B: public A
{
public:
    const A& operator= (const A&)
    {
        std::cout << "B=?\n";
        return *this;
    }
};

int main()
{
    B b, c;
    A* pb = &b;
    A* pc = &c;
    *pb = *pc;
}

---

What's wrong with your sample operator= code? I just ran it, and it runs as expected. The last line in main is what triggers the overloaded = operator. Since the object at *pb is of type B, the vtable points to the correct function.

O_o

Do you think that '?' is there by accident?

Perhaps this update will explain the problem a little better.

Soma

Code:

---

#include <iostream>

class A
{
public:
    virtual const A& operator = (const A&)
    {
        std::cout << "A=A\n";
        return *this;
    }
};

class B: public A
{
public:
    const A& operator= (const A&)
    {
        std::cout << "B=?\n";
        return *this;
    }
};

class C: public A
{
public:
    const A& operator= (const A&)
    {
        std::cout << "C=?\n";
        return *this;
    }
};

int main()
{
    B b;
    C c;
    A* pb = &b;
    A* pc = &c;
    *pb = *pb;
    *pb = *pc;
    *pc = *pb;
    *pc = *pc;
}

---

phantomotap - was your post directed at anon or me?

edit: I don't see what problem you're trying to explain better.

Oh you mean because the = operator doesn't actually assign anything?