C ++运算符<<使用模板重载流[重复]

Question

我正在尝试重载 operatorCExportFunctions 项目中，我可以log << "xxx"。但是，当我尝试在另一个项目 (CCallMethods) 中执行相同操作时，我无法写入文件。编译没问题。没有错误。但是Entered processMessage() 没有被写入文件。有谁能帮忙吗？

Project A - CExportFunctions.h:
#ifdef DLLDIR_EX
   #define DLLDIR  __declspec(dllexport)   // export DLL information
#else
   #define DLLDIR  __declspec(dllimport)   // import DLL information
#endif

...

class DLLDIR CExportFunctions
{
public:
    ...

    ofstream stream;
};

Project A - CExportFunctions.cpp:

#include "CExportFunctions.h"

...

//! write to log file
template<typename T> CExportFunctions& operator<<(CExportFunctions& stream, T val)
{
    ...

    stream.stream.open("D:/Logger/logs.txt", ios::out | ios::app);
    stream.stream << << val << std::endl;
    stream.stream.close();

    return stream;
}

//! save scenario dialog
void CExportFunctions::saveScenario()
{
    CExportFunctions log;
    log << "Entered saveScenario()";

    ...
}

Project B - CCallMethods.cpp:

#include "CExportFunctions.h"

void CCallMethods::processMessage()
{
    ...

    CExportFunctions log;
    log.stream << "Entered processMessage()";
}

Answer 1

您正在调用不同的函数。在您的保存场景中：

//! save scenario dialog
void CExportFunctions::saveScenario()
{
    CExportFunctions log;
    log << "Entered saveScenario()";

    ...
}

你实际上是在打电话给你的

template<typename T> CExportFunctions& operator<<(CExportFunctions& stream, T val)

但这是第二个：

void CCallMethods::processMessage()
{
    ...

    CExportFunctions log;
    log.stream << "Entered processMessage()";
}

您正在调用operator<<(std::ofstream&, const char*)... 这不涉及打开文件。我想你的意思是：

log << "Entered processMessage()";