An iterator connect token is a completion token for completion signature void(error_code, Iterator), where the type Iterator is used in the corresponding async_connect() function.

Examples

A free function as an iterator connect token:

void connect_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::iterator iterator)
{
  ...
}

An iterator connect token function object:

struct connect_handler
{
  ...
  template <typename Iterator>
  void operator()(
      const boost::system::error_code& ec,
      Iterator iterator)
  {
    ...
  }
  ...
};

A lambda as an iterator connect token:

boost::asio::async_connect(...,
    [](const boost::system::error_code& ec,
      boost::asio::ip::tcp::resolver::iterator iterator)
    {
      ...
    });

A non-static class member function adapted to an iterator connect token using std::bind():

void my_class::connect_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::iterator iterator)
{
  ...
}
...
boost::asio::async_connect(...,
    std::bind(&my_class::connect_handler,
      this, std::placeholders::_1,
      std::placeholders::_2));

A non-static class member function adapted to an iterator connect token using boost::bind():

void my_class::connect_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::iterator iterator)
{
  ...
}
...
boost::asio::async_connect(...,
    boost::bind(&my_class::connect_handler,
      this, boost::asio::placeholders::error,
      boost::asio::placeholders::iterator));

Using use_future as an iterator connect token:

std::future<boost::asio::ip::tcp::resolver::iterator> f =
  boost::asio::async_connect(..., boost::asio::use_future);
...
try
{
  boost::asio::ip::tcp::resolver::iterator i = f.get();
  ...
}
catch (const system_error& e)
{
  ...
}

Using use_awaitable as an iterator connect token:

boost::asio::awaitable<void> my_coroutine()
{
  try
  {
    ...
    boost::asio::ip::tcp::resolver::iterator i =
      co_await boost::asio::async_connect(
          ..., boost::asio::use_awaitable);
    ...
  }
  catch (const system_error& e)
  {
    ...
  }
}