轻量aop 一个疑问 about cosmos HOT 4 OPEN

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>
    typename std::enable_if<has_member_Before<Head, Args...>::value && has_member_After<Head, Args...>::value>::type 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)...);
    }

    template <typename Head, typename... Tail>
    typename std::enable_if<!has_member_Before<Head, Args...>::value && has_member_After<Head, Args...>::value>::type Invoke(Args&&... args, Head&& headAspect, Tail&&... tailAspect)
    {

        Invoke(std::forward<Args>(args)..., std::forward<Tail>(tailAspect)...);
        headAspect.After(std::forward<Args>(args)...);
    }

    template <typename Head, typename... Tail>
    typename std::enable_if<has_member_Before<Head, Args...>::value && !has_member_After<Head, Args...>::value>::type Invoke(Args&&... args, Head&& headAspect, Tail&&... tailAspect)
    {
        headAspect.Before(std::forward<Args>(args)...);
        Invoke(std::forward<Args>(args)..., std::forward<Tail>(tailAspect)...);
    }