保罗万象的对象——Variant

对一个对象设置其可容纳的多种类型

通过类型对对象进行Set和Get，类型之间互不影响，一个类型只能又一个值

variant.h

/*
 * variant.h
 *
 *  Created on: 2012-3-9
 *      Author: vivence
 */

#ifndef VARIANT_H_
#define VARIANT_H_

namespace ghost{

template<typename... Tn>
class Variant;

template<>
class Variant<>{};

template<typename T, typename... Tn>
const T& GetVariant(const Variant<T, Tn...>& t);
template<typename T, typename... Tn>
T& GetVariant(Variant<T, Tn...>& t);

template<typename T, typename... Tn>
class Variant<T, Tn...> : public Variant<Tn...>{
    T v_;

public:
    const T& GetValue() const{return v_;}
    T& GetValue(){return v_;}

    template<typename TT>
    const TT& Get() const{return GetVariant<TT>(*this);}
    template<typename TT>
    TT& Get(){return GetVariant<TT>(*this);}
    template<typename TT>
    void Set(const TT& t){Variant<Tn...>::Set(t);}
    void Set(const T& t){v_ = t;}
};

template<typename T, typename... Tn>
const T& GetVariant(const Variant<T, Tn...>& t){return t.GetValue();}
template<typename T, typename... Tn>
T& GetVariant(Variant<T, Tn...>& t){return t.GetValue();}

} // namespace ghost

#endif /* VARIANT_H_ */

 

test.cpp

/*
 * test.cpp
 *
 *  Created on: 2012-3-9
 *      Author: vivence
 */

#include "variant.h"
#include <iostream>
#include <iomanip>

int main()
{
    ghost::Variant<int, bool, char> test;
    test.Set(1);
    test.Set(false);
    test.Set('a');
    test.Set('b');
    std::cout<<test.Get<int>()<<std::endl;
    std::cout<<std::boolalpha<<test.Get<bool>()<<std::endl;
    std::cout<<test.Get<char>()<<std::endl;
    return 0;
}