c++ 面向切面变成 aop 通用模板

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#ifndef AOP_h#define AOP_h#define HAS_MEMBER(member)\template<typename T, typename... Args>struct has_member_##member\{\private:\template<typename U> static auto Check(int) -> decltype(std::declval<U>().member(std::declval<Args>()...), std::true_type()); \template<typename U> static std::false_type Check(...);\public:\enum{value = std::is_same<decltype(Check<T>(0)), std::true_type>::value};\};\HAS_MEMBER(Foo)HAS_MEMBER(Before)HAS_MEMBER(After) template<typename Func, typename... Args>struct Aspect  {Aspect(Func&& f) : m_func(std::forward<Func>(f)){}template<typename T>typename std::enable_if<has_member_Before<T, Args...>::value&&has_member_After<T, Args...>::value>::type Invoke(Args&&... args, T&& aspect){aspect.Before(std::forward<Args>(args)...);//核心逻辑之前的切面逻辑m_func(std::forward<Args>(args)...);//核心逻辑aspect.After(std::forward<Args>(args)...);//核心逻辑之后的切面逻辑}template<typename T>typename std::enable_if<has_member_Before<T, Args...>::value&&!has_member_After<T, Args...>::value>::type Invoke(Args&&... args, T&& aspect){aspect.Before(std::forward<Args>(args)...);//核心逻辑之前的切面逻辑m_func(std::forward<Args>(args)...);//核心逻辑}template<typename T>typename std::enable_if<!has_member_Before<T, Args...>::value&&has_member_After<T, Args...>::value>::type Invoke(Args&&... args, T&& aspect){m_func(std::forward<Args>(args)...);//核心逻辑aspect.After(std::forward<Args>(args)...);//核心逻辑之后的切面逻辑}template<typename Head, typename... Tail>void Invoke(Args&&... args, Head&&headAspect, Tail&&... tailAspect){headAspect.Before(std::forward<Args>(args)...);Invoke(std::forward<Args>(args)..., std::forward<Tail>(tailAspect)...);headAspect.After(std::forward<Args>(args)...);}private:Func m_func; //被织入的函数};template<typename T> using identity_t = T;//AOP的辅助函数，简化调用template<typename... AP, typename... Args, typename Func>void Invoke(Func&&f, Args&&... args){Aspect<Func, Args...> asp(std::forward<Func>(f));asp.Invoke(std::forward<Args>(args)..., identity_t<AP>()...);}#endif // !AOP_h
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