Question

I’m designing a method for an input handler class. Here is some pseudo code…

void InputHandler::ScanEvents( boost::function1< void, std::string& > &func ) {
   // Scan keys, determining string to pass
     // If string found, call func with string as its argument on object tied to func
}

I’m not exactly sure how to implement this, or if it is even possible, since the whole point of a function is to separate it from its caller. The idea is that an object has a private member function and a boost::function member that holds it. Whenever it calls ScanEvents on its InputHandler, it passes that function, so the ScanEvents can “activate it” whenever an appropriate event is found.

Efficiency is a concern, as this is in a domain where performance is important, and this function is called frequently.

P.S. I swear I remember reading an example like this in one of Scott Meyer’s books, but I can’t find it for the life of me. Maybe it was in Modern C++ Design…looking….

Answer 1

Something along the lines of

class Thingy
{
public:
    Thingy() : callback(bind(&Thingy::Callback, this, _1)) {}

    void DoStuff()
    {
        handler.ScanEvents(callback);
    }

private:
    InputHandler handler;
    function<void(string)> callback;

    void Callback(string s)
    {
        cout << "Called with " << s << endl;
    }
};

ought to do what you describe. But it would probably be more efficient for the callback to take the string by reference.