Boost C++ Libraries

Determine if T has the get_executor member function.

Synopsis

Defined in header <boost/beast/core/stream_traits.hpp>

template<
    class T>
using has_get_executor = see-below;

Description

Metafunctions are used to perform compile time checking of template types. This type will be std::true_type if T has the member function with the correct signature, else type will be std::false_type.

Example

Use with tag dispatching:

template < class T>
void maybe_hello(T const & t, std::true_type)
{
    net::post(
        t.get_executor(),
        []
        {
            std::cout << "Hello, world!" << std::endl;
        });
}

template < class T>
void maybe_hello(T const &, std::false_type)
{
    // T does not have get_executor
}

template < class T>
void maybe_hello(T const & t)
{
    maybe_hello(t, has_get_executor<T>{});
}

Use with static_assert:

struct stream
{
    using executor_type = net::io_context::executor_type;
    executor_type get_executor() noexcept;
};

static_assert(has_get_executor<stream>::value, "Missing get_executor member");