Does f(int) in base class inherited in derived derived class D which have f(double)?

Question

Possible Duplicate:
Why does an overridden function in the derived class hide other overloads of the base class?

Does f(int) in base class inherited in derived derived class D? if yes then why overloading is not working here. and if no then why f(int) is not inherited as class d is publicly derived. I am confused.

    class B {
    public:
        int f(int i) { cout << "f(int): "; return i+1; }
        // ...
    };

    class D : public B {
    public:
        double f(double d) { cout << "f(double): "; return d+1.3; }
        // ...
    };

    int main()
    {
        D* pd = new D;

        cout << pd->f(2) << '\n';
        cout << pd->f(2.3) << '\n';
    }

What is "not working"? What do you see, and what do you expect to see? — Mooing Duck, Sep 22 '11 at 17:37
it is calling f(double) both times.so i think f(int) is not inherited.But why it is not inherited? — Suri, Sep 22 '11 at 17:39
Also FAQ: http://www.parashift.com/c++-faq-lite/strange-inheritance.html#faq-23.9 — AnT stands with Russia, Sep 22 '11 at 17:47

Alok Save · Answer 1 · 2011-09-22T18:01:36.990

This is the Classical example for Function Hiding.
The overload resolution in C++ does not work across classes, A function in derived class Hides all the functions with identical name in the Base class. Compiler only sees the function in derived class for an derived class object.

You can Unhide all the base class functions for your derived class by using the using Declaration. in your derive class.

Adding,

using B::f;

in your derived class will enable your derived class object to access all the functions with the name f() int the Base class as if they were overloaded functions in Derived class.

This should be a good read:

What's the meaning of, Warning: Derived::f(char) hides Base::f(double)?

score 4 · Answer 2 · answered Sep 22 '11 at 17:41

I think if you give a derived class a function with the same name as functions existing in a base class, the derived class' function will hide the base class' functions. If you merely wanted to overload, use the using keyword.

class B {
public:
    int f(int i) { cout << "f(int): "; return i+1; }
    // ...
};

class D : public B {
public:
    using B::f; //brings in all of B's "f" functions
                //making them equals of D's "f" functions.
    double f(double d) { cout << "f(double): "; return d+1.3; }
    // ...
};

int main()
{
    D* pd = new D;

    cout << pd->f(2) << '\n';
    cout << pd->f(2.3) << '\n';
}

Does f(int) in base class inherited in derived derived class D which have f(double)?

2 Answers2