C++；纯虚函数模板类的语法？ 我只熟悉C++模板，而对模板类添加纯虚函数已经耗尽了满足编译器的能力。

下面的代码

#include <iostream>
#include <string>
#include <sstream>

class Pearl
{
    public:
        Pearl(int value);
        virtual ~Pearl();

    protected:
        int mValue;
};

Pearl::Pearl(int value)
    : mValue(value)
{
    std::cout << "$" << mValue << " Pearl created" << std::endl;
}

Pearl::~Pearl()
{
    std::cout << "$" << mValue << " Pearl destroyed" << std::endl;
}

///////////////////////////////////////////////////////////////////////

class Oyster
{
    public:
        Oyster(std::string str, int value);
        virtual ~Oyster();

    protected:
        Pearl mPearl;
        std::string mName;

    friend class OStreamer;
};

Oyster::Oyster(std::string name, int value)
    : mName(name)
    , mPearl(value)
{
    std::cout << "Oyster " << mName << " created" << std::endl;
}

Oyster::~Oyster()
{
    std::cout << "Oyster " << mName << " destroyed" << std::endl;
}

///////////////////////////////////////////////////////////////////////

template <typename T> class Streamer
{
    public:
        Streamer(T& rT, unsigned int flags);
        ~Streamer();

        virtual std::ostream Display() = 0;

        static const unsigned int A = 0x1;
        static const unsigned int B = 0x2;

    protected:
        T& mrT; // Aah pity the foo!
        unsigned int mFlags;

    friend class OStreamer;
};

///////////////////////////////////////////////////////////////////////

class OStreamer : public Streamer<Oyster>
{
    public:
        OStreamer(Oyster oyster, unsigned int flags);
        virtual std::ostream Display();
};

OStreamer::OStreamer(Oyster oyster, unsigned int flags)
    : Streamer<Oyster>(oyster, flags)
{
}

std::ostream OStreamer::Display()
{
    std::ostringstream oss;

    oss << "Oyster[" << mrT.mName << "]" << std::endl;
}

///////////////////////////////////////////////////////////////////////

template <typename T> std::ostream& operator<<(std::ostream& os, const Streamer<T> streamer)
{
    return os;
}

///////////////////////////////////////////////////////////////////////

int main()
{
    Oyster sam("Sam", 50);

    std::cout << OStreamer(sam, OStreamer::A) << std::endl;

    return 0;
}

#包括
#包括
#包括
珍珠级
{
公众：
珍珠（整数值）；
虚拟珍珠（）；
受保护的：
int值；
};
珍珠：珍珠（整数）
：mValue（值）
{
std:：cout将操作员过载更改为：

template <typename T> std::ostream& operator<<(std::ostream& os,
                           const Streamer<T> &streamer)
{
    return os;
}

template std:：ostream&operator我敢打赌。+1D'oh！我盯着代码看了太久，完全掩盖了这一点。我谦恭地接受我公开的尴尬。：）谢谢你，@sam varshavchik！
template <typename T> std::ostream& operator<<(std::ostream& os,
                           const Streamer<T> &streamer)
{
    return os;
}