template<typename _Tp, _Tp __v>    struct integral_constant    {      static const _Tp                      value =http://www.mamicode.com/ __v;      typedef _Tp                           value_type;      typedef integral_constant<_Tp, __v>   type;    };    /// typedef for true_type  typedef integral_constant<bool, true>     true_type;  /// typedef for false_type  typedef integral_constant<bool, false>    false_type;template<typename, typename>    struct is_same    : public false_type { };  template<typename _Tp>    struct is_same<_Tp, _Tp>    : public true_type { };

  1 struct A{~A(){cout<<"delete A..."<<endl;}};  2 template<typename T>  3 struct TypeTraits  4 {  5        typedef void TYPE;  6 };  7 template<>  8 struct TypeTraits<std::string>  9 { 10        typedef std::string TYPE; 11 }; 12 template<> 13 struct TypeTraits<long> 14 { 15        typedef long TYPE; 16 }; 17 template<> 18 struct TypeTraits<A> 19 { 20        typedef A TYPE; 21 }; 22 template<> 23 struct TypeTraits<double> 24 { 25  26        typedef double TYPE; 27 }; 28  29  30 class DeleteLong 31 { 32 public: 33     void operator()(void *p) 34     { 35         delete static_cast<long*>(p); 36     } 37 }; 38 class DeleteString 39 { 40 public: 41     void operator()(void *p) 42     { 43         delete static_cast<string*>(p); 44     } 45 }; 46 class DeleteDouble 47 { 48 public: 49     void operator()(void *p) 50     { 51         delete static_cast<double*>(p); 52     } 53 }; 54 class DeleteA 55 { 56 public: 57     void operator()(void *p) 58     { 59         delete static_cast<A*>(p); 60     } 61 }; 62  63 class ExportData 64 { 65     void* vp; 66     enum my_type {SP,LP,DP,AP} types; 67     static unordered_map<type_index,my_type> typeMap; 68     static vector<function<void(void*)>> deleters; 69 public: 70  71     template <typename T> ExportData(const T& t) 72     { 73         static_assert(is_same<typename TypeTraits<T>::TYPE,T>::value,"not support!"); 74         vp=new T(t); 75         types= typeMap[typeid(T)]; 76     } 77     template <typename T> void setData(const T& t) 78     { 79         static_assert(is_same<typename TypeTraits<T>::TYPE,T>::value,"not support!"); 80         assert(types==typeMap[typeid(T)]); 81         *(static_cast<T*>(vp))=t; 82     } 83     template <typename T> void getData(T& t) 84     { 85         static_assert(is_same<typename TypeTraits<T>::TYPE,T>::value,"not support!"); 86         assert(types==typeMap[typeid(T)]); 87         t=*(static_cast<T*>(vp)); 88     } 89  90     ~ExportData() 91     { 92        (deleters[types])(vp); 93     } 94  95 }; 96  97 unordered_map<type_index,ExportData::my_type> ExportData::typeMap 98 { 99     {typeid(string),ExportData::my_type::SP},100     {typeid(long),ExportData::my_type::LP},101     {typeid(double),ExportData::my_type::DP},102     {typeid(A),ExportData::my_type::AP}103 };104 vector<function<void(void*)>> ExportData::deleters {DeleteString(),DeleteLong(),DeleteDouble(),DeleteA()};