C++ 超载<&书信电报；运算符并将参数传递到std:：cout

我想创建一个用于日志记录的类，其行为类似于

std:：cout

，但会自动向流中插入附加信息

我想要的示例用法如下（现在不必关心对象和上下文类型，只需假设它们是std:：string）：

我一直在尝试：

template<typename T>
Logger& operator << (const T& msg){
    std::cout << timestamp() << msg << std::endl << std::flush;
    return *this;
}

模板
Logger&operator您的代码不起作用的原因是您没有实现
operator如果您愿意，您当然可以重载流类，只要
operator
std:：endl
已经刷新流。请参阅：请提供整个（精简但完整）代码以进行复制。然后，不要解释错误，也要引用它。很可能您正在临时或常量
记录器上使用它，或者尝试将重载函数（如
std:：endl
）流式传输到其中，但是如果没有实际的代码和错误，这是不可能的。Loki，这几乎解决了我的问题，谢谢！
[timestamp] Event with object : [obj_desc] while in context : [this context][eol][flush]

template<typename T>
Logger& operator << (const T& msg){
    std::cout << timestamp() << msg << std::endl << std::flush;
    return *this;
}

Logger l;
l << "Event with object : " << obj << " while in context : " << context;

Logger l;
l.operator<<("Event with object : ").operator<<(obj).operaator<<(" while in context : ").operator<<(context);

struct LoggerStream
{
    std::ostringstream strm;

    struct Timestamp
    {
    };

    ~LoggerStream()
    {
        std::string s = strm.str();
        if (!s.empty())
            std::cout << s << std::flush;
    }

    LoggerStream& operator<< (const Timestamp &t)
    {
        strm << "[timestamp] "; // format this however you need
        return *this;
    }

    LoggerStream& operator<< (const object &obj)
    {
        strm << "[obj_desc]"; // format this however you need
        return *this;
    }

    LoggerStream& operator<< (const context &ctx)
    {
        strm << "[this context]"; // format this however you need
        return *this;
    }

    LoggerStream& operator<< (std::ostream&(*f)(std::ostream&))
    {
        if (f == (std::basic_ostream<char>& (*)(std::basic_ostream<char>&)) &std::flush)
        {
            std::string s = strm.str();
            if (!s.empty())
                std::cout << s << std::flush;
            strm.str("");
            strm.clear();
        }
        else
            strm << f;

        return *this;
    }

    template<typename T>
    LoggerStream& operator<< (const T& value)
    {
        strm << value;
        return *this;
    }
};

class Logger
{
    LoggerStream getStream()
    {
        LoggerStream strm;
        strm << Timestamp;
        return strm;
    }
};

Logger l;
l.getStream() << "Event with object : " << obj << " while in context : " << context;
...
l.getStream() << "Event with object : " << obj << " while in context : " << context;
...

Logger l;
LoggerStream strm = l.getStream();
strm << "Event with object : " << obj << " while in context : " << context << std::flush;
...
strm << Logger::Timestamp << "Event with object : " << obj << " while in context : " << context << std::flush;
...

struct Logger
{
    std::ostringstream strm;

    ~Logger()
    {
        std::string s = strm.str();
        if (!s.empty())
            std::cout << "[timestamp] " << s << std::flush;
    }

    Logger& operator<< (const object &obj)
    {
        strm << "[obj_desc]"; // format this however you need
        return *this;
    }

    Logger& operator<< (const context &ctx)
    {
        strm << "[this context]"; // format this however you need
        return *this;
    }

    Logger& operator<< (std::ostream&(*f)(std::ostream&))
    {
        if (f == (std::basic_ostream<char>& (*)(std::basic_ostream<char>&)) &std::flush)
        {
            std::string s = strm.str();
            if (!s.empty())
                std::cout << "[timestamp] " << s << std::flush;
            strm.str("");
            strm.clear();
        }
        else
            strm << f;

        return *this;
    }

    template<typename T>
    Logger& operator<< (const T& value)
    {
        strm << value;
        return *this;
    }
};

Logger() << "Event with object : " << obj << " while in context : " << context;
...
Logger() << "Event with object : " << obj << " while in context : " << context;
...

Logger l;
l << "Event with object : " << obj << " while in context : " << context << std::flush;
...
l << "Event with object : " << obj << " while in context : " << context << std::flush;
...

#include <iostream>
#include <iomanip>
#include <sstream>
#include <ctime>
#include <unistd.h>

#define logcout std::cout << timestamp()

std::string timestamp(void) {
    time_t now = time(0);
    struct tm *tmx = localtime(&now);
    std::ostringstream oss;
    oss << '['
        << (tmx->tm_year+1900)
        << '-'
        << std::setfill('0') << std::setw(2) << (tmx->tm_mon+1)
        << '-'
        << std::setfill('0') << std::setw(2) << (tmx->tm_mday)
        << ' '
        << std::setfill('0') << std::setw(2) << (tmx->tm_hour)
        << ':'
        << std::setfill('0') << std::setw(2) << (tmx->tm_min)
        << ':'
        << std::setfill('0') << std::setw(2) << (tmx->tm_sec)
        << "] ";
    return oss.str();
}

int main (int argc, char *argv[]) {
    logcout << "A slightly\n";
    sleep (5);
    logcout << "sneaky" << " solution\n";
    return 0;
}

[2015-05-26 13:37:04] A slightly
[2015-05-26 13:37:09] sneaky solution

#define logcout std::cout << timestamp()