...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
A resolve handler must meet the requirements for a 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 ip::basic_resolver<>
which is used to initiate the asynchronous operation.
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));