| // last_value function object (documented as part of Boost.Signals) |
| |
| // Copyright Frank Mori Hess 2007. |
| // Copyright Douglas Gregor 2001-2003. Use, modification and |
| // distribution is subject to 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) |
| |
| // For more information, see http://www.boost.org |
| |
| #ifndef BOOST_SIGNALS2_LAST_VALUE_HPP |
| #define BOOST_SIGNALS2_LAST_VALUE_HPP |
| |
| #include <boost/optional.hpp> |
| #include <boost/signals2/expired_slot.hpp> |
| #include <boost/throw_exception.hpp> |
| #include <stdexcept> |
| |
| namespace boost { |
| namespace signals2 { |
| |
| // no_slots_error is thrown when we are unable to generate a return value |
| // due to no slots being connected to the signal. |
| class no_slots_error: public std::exception |
| { |
| public: |
| virtual const char* what() const throw() {return "boost::signals2::no_slots_error";} |
| }; |
| |
| template<typename T> |
| class last_value { |
| public: |
| typedef T result_type; |
| |
| template<typename InputIterator> |
| T operator()(InputIterator first, InputIterator last) const |
| { |
| if(first == last) |
| { |
| boost::throw_exception(no_slots_error()); |
| } |
| optional<T> value; |
| while (first != last) |
| { |
| try |
| { |
| value = *first; |
| } |
| catch(const expired_slot &) {} |
| ++first; |
| } |
| if(value) return value.get(); |
| boost::throw_exception(no_slots_error()); |
| } |
| }; |
| |
| template<> |
| class last_value<void> { |
| public: |
| typedef void result_type; |
| template<typename InputIterator> |
| result_type operator()(InputIterator first, InputIterator last) const |
| { |
| while (first != last) |
| { |
| try |
| { |
| *first; |
| } |
| catch(const expired_slot &) {} |
| ++first; |
| } |
| return; |
| } |
| }; |
| } // namespace signals2 |
| } // namespace boost |
| #endif // BOOST_SIGNALS2_LAST_VALUE_HPP |