override virtual function with the same name

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I can override virtual function with the same name like this:

C++

class I
{
public:
    virtual void foo() = 0;
};

class J
{
public:
    virtual void foo() = 0;
};

class C : public I, public J
{
public:
    virtual void I::foo() { cout << "I" << endl; }
    virtual void J::foo() { cout << "J" << endl; }
};

But when I move the two function out of the class,like this:

C++

class C : public I, public J
{
public:
    virtual void I::foo();
    virtual void J::foo();
};
void C::I::foo() { cout << "I" << endl; }
void C::J::foo() { cout << "J" << endl; }

I got two error say 'foo' not declared in 'C'.
Is there a way to implement the two functions out of the class?

Posted 5-Mar-12 19:32pm

Dnkuni

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tolw · Accepted Answer · 2012-03-05T19:44:00

No, you can't do it directly. There are ways around this limitation however. You would have to introduce an intermediate step:

//DECLARATION
class C : public I, public J
{
public:
    virtual void I::foo() { fooI(); }
    virtual void J::foo() { fooJ(); }

    void fooI();
    void fooJ();
};

//IMPLEMENTATION
void C::fooI() { cout << "I" << endl; }
void C::fooJ() { cout << "J" << endl; }

It isn't exactly pretty, but AFAIK it's the best way to do what you need.