#include <boost/signals2.hpp>
#include <boost/bind.hpp>


class A
{
	//callback
	using callback = typename boost::signals2::signal<void( bool )>::slot_type ;

public :
	//register the callback
	boost::signals2::scoped_connection callback_register( callback cbk )
									__attribute__( ( warn_unused_result ) ) ;

	int getx() __attribute__( ( warn_unused_result ) ) ;

	//callbacks
	boost::signals2::signal<void( bool )>	callbacks ;
} ;

boost::signals2::scoped_connection A::callback_register( callback cbk )
{
	return std::move( callbacks.connect( cbk ) ) ;
}

int A::getx()
{
	int	y = 200 ;
	return y ;
}

void callback()
{
}

int main()
{
	A	a1 ;

	a1.callback_register( boost::bind( &callback ) ) ;
	a1.getx() ;

	return 0 ;
}