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- [/
- / Copyright (c) 2003-2019 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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