Crow：Middlewares 庖丁解牛4 partial_context-CSDN博客

基于partial_context再来解释context

namespace detail
{template<typename... Middlewares>struct partial_context : public pop_back<Middlewares...>::template rebind<partial_context>, public last_element_type<Middlewares...>::type::context{using parent_context = typename pop_back<Middlewares...>::template rebind<detail::partial_context>;template<int N>using partial = typename std::conditional<N == sizeof...(Middlewares) - 1, partial_context, typename parent_context::template partial<N>