Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards


// Example program for connecting an extended slot,
// using a signal's connect_extended and extended_slot_type.
// Copyright Frank Mori Hess 2009.
// Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// For more information, see

#include <boost/signals2/signal.hpp>
#include <iostream>
#include <string>

namespace bs2 = boost::signals2;

void single_shot_slot(const bs2::connection &conn, const std::string &message)
  std::cout << message;

int main()
  typedef bs2::signal<void (void)> sig_type;
  sig_type sig;
    sig_type::extended_slot_type hello(&single_shot_slot, _1, "Hello");
  sig();  // prints "Hello"
    sig_type::extended_slot_type world(&single_shot_slot, _1, ", World!\n");
  sig();  // only prints ", World!\n" since hello slot has disconnected itself
  sig();  // prints nothing, world slot has disconnected itself

  return 0;