继 c++ set 重载无法正确调用，给了一个完整的 demo

// buffer

#ifndef __Buffer_H__
#define __Buffer_H__

#include <iostream>

#include <vector>
#include <list>
#include <deque>
#include <map>
#include <set>

class CBuffer
{
public:
    CBuffer()
    {

    }

    ~CBuffer()
    {

    }

    template <class T>
    CBuffer& operator<<(T &val)
    {
        std::cout << "11111" << std::endl;
        return *this;
    }

    CBuffer& operator<<(std::string &val)
    {
        std::cout << "22222" << std::endl;
        return *this;
    }

    template <class T>
    CBuffer& operator<<(std::list<T> &val)
    {
        auto iter = val.begin();
        while (iter != val.end())
        {
            *this << (*iter++);
        }
        return *this;
    }

    template <class T>
    CBuffer& operator<<(std::deque<T> &val)
    {
        auto iter = val.begin();
        while (iter != val.end())
        {
            *this << (*iter++);
        }
        return *this;
    }

    template <class T>
    CBuffer& operator<<(std::vector<T> &val)
    {
        for (size_t i = 0; i < val.size(); ++i)
        {
            *this << val[i];
        }
        return *this;
    }

    template <class T>
    CBuffer& operator<<(std::set<T> &val)
    {
        auto iter = val.begin();
        while (iter != val.end())
        {
            // static_cast<T> 不加上这个无法正确重载，原因未知
            *this << (*iter++);
        }
        return *this;
    }
};

#endif

// main

#include <iostream>

#include "Buffer.h"

using namespace std;

int main()
{
    CBuffer buf;

    std::set<std::string> a1 = { "aaa"};
    std::vector<std::string> a2 = { "aaa"};
    std::list<std::string> a3 = { "aaa" };
    std::deque<std::string> a4 = { "aaa" };

    buf << a1 << a2 << a3 << a4;

    system("pause");

    return 0;
}

输出

set 的<<重载调用与其他 vector，list，deque 不同。不解！！！