A resolve token is a completion token for completion signature void(error_code, ip::basic_resolver_results<InternetProtocol>), for a specified InternetProtocol.

Examples

A free function as a resolve token:

void resolve_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::results_type results)
{
  ...
}

A resolve token function object:

struct resolve_handler
{
  ...
  void operator()(
      const boost::system::error_code& ec,
      boost::asio::ip::tcp::resolver::results_type results)
  {
    ...
  }
  ...
};

A lambda as a resolve token:

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

A non-static class member function adapted to a resolve token using std::bind():

void my_class::resolve_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::results_type results)
{
  ...
}
...
resolver.async_resolve(...,
    std::bind(&my_class::resolve_handler,
      this, std::placeholders::_1,
      std::placeholders::_2));

A non-static class member function adapted to a resolve token using boost::bind():

void my_class::resolve_handler(
    const boost::system::error_code& ec,
    boost::asio::ip::tcp::resolver::results_type results)
{
  ...
}
...
resolver.async_resolve(...,
    boost::bind(&my_class::resolve_handler,
      this, boost::asio::placeholders::error,
      boost::asio::placeholders::results));

Using use_future as a resolve token:

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

Using use_awaitable as a resolve token:

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