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[/
/ Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
/
/ Distributed under the Boost Software License, Version 1.0. (See accompanying
/ file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
/]
[section:ResolveHandler Resolve handler requirements]
A resolve handler must meet the requirements for a [link boost_asio.reference.Handler
handler]. A value `h` of a resolve handler class should work correctly in the
expression `h(ec, r)`, where `ec` is an lvalue of type `const error_code` and
`r` is an lvalue of type `const ip::basic_resolver_results<InternetProtocol>`.
`InternetProtocol` is the template parameter of the [link
boost_asio.reference.ip__basic_resolver `ip::basic_resolver<>`] which is used to
initiate the asynchronous operation.
[heading Examples]
A free function as a resolve handler:
void resolve_handler(
const boost::system::error_code& ec,
boost::asio::ip::tcp::resolver::results_type results)
{
...
}
A resolve handler 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 handler:
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 handler 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 handler 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));
[endsect]
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