c++11 Any

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#include <iostream>#include <string>#include <type_traits>#include <utility>#include <stdexcept>#include <typeindex>#include <exception>using namespace std;struct Any{    Any(void) : m_tpIndex(std::type_index(typeid(void))) {}    Any(const Any& that) : m_ptr(that.Clone()), m_tpIndex(that.m_tpIndex) {}    Any(Any && that) : m_ptr(std::move(that.m_ptr)), m_tpIndex(that.m_tpIndex) {}    //建立智能指標時，對於一般的類型，通過std::decay來移除引用和cv符，從而擷取原始類型    template<typename U, class = typename std::enable_if<!std::is_same<typename std::decay<U>::type, Any>::value, U>::type>     Any(U && value)         : m_ptr(new Derived < typename std::decay<U>::type>(std::forward<U>(value)))        , m_tpIndex(std::type_index(typeid(typename std::decay<U>::type))) {}    bool IsNull() const { return !bool(m_ptr); }    template<class U> bool Is() const    {        return m_tpIndex == std::type_index(typeid(U));    }    //將Any轉換為實際的類型    template<class U>    U& AnyCast()    {        if (!Is<U>())        {            std::cout << "can not cast " << typeid(U).name() << " to " << m_tpIndex.name() << std::endl;            //throw std::logic_error{ "bad cast" };        }         else {            auto derived = dynamic_cast<Derived<U>*> (m_ptr.get());            return derived->m_value;        }    }    Any& operator=(const Any& a)    {        if (m_ptr == a.m_ptr)            return *this;        m_ptr = a.Clone();        m_tpIndex = a.m_tpIndex;        return *this;    }private:    struct Base;    typedef std::unique_ptr<Base> BasePtr;    struct Base    {        virtual ~Base() {}        virtual BasePtr Clone() const = 0;    };    template<typename T>    struct Derived : Base    {        template<typename U>        Derived(U && value) : m_value(std::forward<U>(value)) { }        BasePtr Clone() const        {            return BasePtr(new Derived<T>(m_value));        }        T m_value;    };    BasePtr Clone() const    {        if (m_ptr != nullptr)            return m_ptr->Clone();        return nullptr;    }    BasePtr m_ptr;    std::type_index m_tpIndex;};int main(int argc, char *argv[]){    map<string, Any> one;    one["one"] = 1;    one["two"] = 1.2;    one["three"] = "hello";    one["four"] = string("word");    vector<int> two = { 1, 2, 3, 4, 5 };    one["five"] = two;    cout << one["one"].AnyCast<int>() << endl;    cout << one["two"].AnyCast<double>() << endl;    cout << one["three"].AnyCast<const char*>() << endl;    cout << one["four"].AnyCast<string>() << endl;        vector<int> tmp = one["five"].AnyCast< vector<int> >();    for (auto it = tmp.begin(); it != tmp.end(); ++it) {        cout << *it << endl;    }    getchar();    return 0;}

 

c++11 Any