C++ (Qt)typedef type_list< double, int, std::string, float > list_of_types; struct cals_sum : public any_visitor< double, list_of_types >{ double m_sum; cals_sum () : m_sum() {} double operator()( const std::string & str ) { return m_sum += std::stod(str); } template <class T> double operator()( const T & val ) { return m_sum += double( val ); }}; struct to_string : public any_visitor< std::string, list_of_types >{ std::string operator()( const std::string & str ) const { return str; } template <class T> std::string operator()(const T & val) const { return std::to_string(val); }}; int main(){ std::list< boost::any > many = {123, 3.14, 5.6f, std::string("2.71")}; cals_sum visitor; for ( const auto & x : many ) apply_any_visitor( visitor, x ); std::cout << visitor.m_sum << std::endl; return 0;}
C++ (Qt)template <class Visitor, class TypeList>struct any_cast_helper{ static typename Visitor::result_type get(const boost::any & any, Visitor & visitor) { if (any.type() == typeid(typename TypeList::first_type)) return visitor(boost::any_cast<typename TypeList::first_type >(any)); return any_cast_helper<Visitor, typename TypeList::next_type_list>::get(any, visitor); } static typename Visitor::result_type get(const boost::any & any, const Visitor & visitor) { if (any.type() == typeid(typename TypeList::first_type)) return visitor(boost::any_cast<typename TypeList::first_type>(any)); return any_cast_helper<Visitor, typename TypeList::next_type_list>::get(any, visitor); }}; template <class Visitor>struct any_cast_helper<Visitor, null_type>{ static typename Visitor::result_type get(const boost::any &, Visitor &) throw(std::bad_cast) { throw std::bad_cast(); } static typename Visitor::result_type get(const boost::any &, const Visitor &) throw(std::bad_cast) { throw std::bad_cast(); }}; template <class Visitor>typename Visitor::result_type apply_any_visitor(const Visitor & visitor, const boost::any & any){ return any_cast_helper<Visitor, typename Visitor::type_list>::get(any, visitor);} template <class Visitor>typename Visitor::result_type apply_any_visitor( Visitor & visitor, const boost::any & any){ return any_cast_helper<Visitor, typename Visitor::type_list>::get(any, visitor);}
C++ (Qt)template <class Stream>struct serialize : public any_visitor<void, type_list<int, uint, float, bool, ARGB>>{ serialize(Stream & out) : m_out(out) {} template <class T> void operator()(const T & val) { m_out << val; } private: Stream & m_out;};
C++ (Qt)static typename Visitor::result_type get(const boost::any & any, Visitor visitor)
C++ (Qt)class serializator{public: serializator(std::ofstream & out) : m_out(out) {} template <class T> friend serializator & operator<<(serializator &, const T &); friend serializator & operator<<(serializator &, bool); private: int bool_packet; std::ofstream & m_out;};
C++ (Qt)struct editor : public any_visitor<void, type_list<int, double, std::string>>{ void operator()(std::string & s) { s += " Qt5"; } void operator()(int & i) { i += 100500; } void operator()(double & d) { d = 3.14159; }}; struct printer : public any_visitor<void, type_list<int, double, std::string>>{ template <class T> void operator()(const T & val) const { std::cout << val << std::endl; }}; int main(){ std::list<boost::any> many = {13, 1.34834657, std::string("hello")}; std::cout << "before:" << std::endl; for (auto & x : many) apply_any_visitor(printer(), x); for (auto & x : many) apply_any_visitor(editor(), x); // Editor изменяет значения элементов. std::cout << "after:" << std::endl; for (auto & x : many) apply_any_visitor(printer(), x); return 0;}
