New subject: [Boost-Users] question about boost::bind

22 May 2003

      First, the working code:

#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <iostream>
#include <string>
#include <map>

using namespace std;

struct message
{
    string mtablename;
    unsigned long long mpk;
    message(const string& tablename, const unsigned long long pk) : 
mtablename(tablename), mpk(pk) { }
};

typedef boost::function < void, unsigned long long > MessageFunctor;
typedef multimap < string, MessageFunctor > MessageFunctorMap;
typedef pair < MessageFunctorMap::iterator, 
MessageFunctorMap::iterator > MessageFunctorTableMapIteratorPair;

void callfunctor(pair < string, MessageFunctor > item, unsigned long 
long pk)
{
        item.second(pk);
}

class MessageCenter
{
    MessageFunctorMap mHandlerMap;

    public:

    MessageCenter() { }

    void sendMessage(message& amessage)
    {   
        MessageFunctorTableMapIteratorPair iterPair = 
mHandlerMap.equal_range(amessage.mtablename);
        std::for_each(iterPair.first, iterPair.second, boost::bind
(&callfunctor, _1, amessage.mpk)); // QUESTION LINE
    }

    void addHandler(string tableName, MessageFunctor handler)
    {   
        mHandlerMap.insert(make_pair(tableName, handler));
    }
};

int gFooCounter = 0;
void fooHandler(unsigned long long x)
{
    cout << "fooHandler called on pk=" << x << endl;
    gFooCounter++;
}

void gooHandler(unsigned long long x){}

int main(int argc, const char** argv)
{
    MessageCenter messageCenter;

    messageCenter.addHandler("foo", fooHandler);
    messageCenter.addHandler("foo", fooHandler);
    messageCenter.addHandler("goo", gooHandler);

    // send some messages
    message fooMessage("foo", 123);
    messageCenter.sendMessage(fooMessage);

    if(gFooCounter != 2)
        cerr << "something didn't work";
    else
        cout << "everything worked..." << endl;

    return 0;
}

now for the question:

on the line labeled "QUESTION LINE", you can see that I'm
binding to 
a functor called "callfunctor".  All callfunctor does is call
the 
functor embedded in the map's pair.  

Is there a way to simplify the line in question so that I don't
need 
to create the functor just to get access to the pair.second member?

-Darin

question about boost::bind

Darin Buck

Peter Dimov

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