delegate implementation c++, how to find specific class member function

Question

I am studying how to implement simple delegates with c++11. The problem the disconnect-method, I would like to target specific function of specific object to be removed from the map. With this implementation, i erase all functions connected to specific object instance. Id like to be able to do something like :

delegate.disconnect (myobj, &MyObj::method)

instead of

delegate.disconnect (myobj)

which erases all connceted functions for myobj.

template <typename ... Params >
class Delegate {

private:    
    typedef std::function < void (Params...)> FunctionType;
    std::map < void*, std::vector < FunctionType >> m_functions;

public:
    template <typename Class>
    void connect(Class& obj, void (Class::*func) (Params...) ) 
    {
        std::function < void (Class, Params...) >  f = func;
        FunctionType fun = [&obj, f](Params... params) { f(obj, params...); };
        m_functions[&obj].push_back(fun);
    }

    template <typename Class>
    void disconnect(Class& obj) {
        m_functions.erase(&obj);
    }

    template <typename ... Args>
    void operator() (Args...args)
    {       
        for (auto& pair : m_functions) {
            for (auto& func : pair.second) {
                func(args...);
            }
        }
    }
};

Answer 1

I found a way to hash member function which is what i need so i am answering my own question here:

template <typename Class>
size_t getHash(void (Class::*func) (Params...)) {
    const char *ptrptr = static_cast<const char*>(static_cast<const void*>(&func));
    int size = sizeof (func);
    std::string str_rep(ptrptr, size);
    std::hash<std::string> strHasher;
    return strHasher(str_rep);
}

usage is now simple:

delegate.disconnect(&MyClass::MyFunc);

reference: How to hash and compare a pointer-to-member-function?