Re: is it possible to get a unique key for a (instance, method) pair?

From:

t.lehmann@rtsgroup.net

Newsgroups:

comp.lang.c++.moderated

Date:

18 Dec 2006 11:46:16 -0500

Message-ID:

<1166429052.386363.3320@79g2000cws.googlegroups.com>

    template < class T >
    struct Wrapper
    {
        typedef void (T::*Simple_Method)();

        // static factory method
        template < Simple_Method SM >
        static Wrapper* Get()
        {
            static Wrapper sWrapper(SM);

            return &sWrapper;
        }

        // less than comparison
        bool operator<( const Wrapper& rhs ) const
        {
            return std::less<Wrapper>()( this, &rhs );
        }

        // invoke wrapped member function
        void operator()( T& t)
        {
            &t->*mf();
        }

    private:
        Wrapper(Simple_Method inMF) : mf(inMF) {}

        Simple_Method mf;
    };

    typedef Wrapper<X> WrapperX, * WrapperXPtr;

    int main()
    {
        WrapperXPtr testOne = WrapperX::Get< &X::test1 >();
        WrapperXPtr testTwo = WrapperX::Get< &X::test2 >();

        testOne < testTwo; // OK
    }

Well, you example is working fine - still one question ... How do I've
to implement this class for wrapping any method instance? See my code
(the compiler is yelling about the line inside of 'make_dummy_instance'
- can you help?

class DummyInstanceBase
{
    public:
        DummyInstanceBase(){}
        virtual ~DummyInstanceBase(){}
};

template <class T>
class DummyInstance : public DummyInstanceBase
{
    public:
        template <T RealInstance>
        static DummyInstanceBase* get()
        {
            static DummyInstance instance;
            return &instance;
        }
};

template <class T>
DummyInstanceBase* make_dummy_instance(const T& instance)
{
    return DummyInstance<T>::get<instance>();
}

// -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
int main()
{
    DummyInstanceBase* instOne = make_dummy_instance(&X::test1);
}

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