需要将 String^ 转换为 char * [英] Need to convert String^ to char *

问题描述

我正在使用 .NET DateTime 来获取当前日期和时间.我将其转换为字符串以用作文件名的一部分.问题是保存图像的 OpenCV 命令需要 char * 而不是字符串类型，而 DateTime 只会输出 String^ 类型.我该如何进行这项工作?这里的代码没有完成

I am using the .NET DateTime to get the current date and time. I am converting it to a string to use as part of a file name. The problem is the OpenCV command to save an image requires a char * not a string type, and DateTime will only output a String^ type. How do I make this work? Heres the code not completed

String^ nowString = DateTime::Now.ToString("yyyy-MM-dd-HH:mm");
        IplImage* toSave;
        CvCapture* capture = cvCreateCameraCapture(0);
        toSave = cvQueryFrame( capture );
        cvSaveImage(nowString, toSave);
        cvReleaseImage(&toSave);
        cvReleaseCapture(&capture);

推荐答案

最好的办法是使用 StringToHGlobalAnsi.这是完整的代码，展示了它是如何完成并记住释放分配的内存的.

Your best bet is to use StringToHGlobalAnsi. Here is complete code showing how its done and remembering to free the memory allocated.

using namespace System::Runtime::InteropServices;

void MethodName()
{
    String^ nowString = DateTime::Now.ToString("yyyy-MM-dd-HH:mm");
    IntPtr ptrToNativeString = Marshal::StringToHGlobalAnsi(nowString);
    try
    {
        CvCapture* capture = cvCreateCameraCapture(0);
        IplImage* toSave = cvQueryFrame(capture);
        cvSaveImage(static_cast<char*>(ptrToNativeString.ToPointer()), toSave);
        cvReleaseImage(&toSave);
        cvReleaseCapture(&capture);
    }
    catch (...)
    {
        Marshal::FreeHGlobal(ptrToNativeString);
        throw;
    }
    Marshal::FreeHGlobal(ptrToNativeString);
}

您可能需要重新考虑在文件名中使用:"字符，因为我不相信 windows 非常喜欢这个.

You might want to rethink using a ':' character in the filename, as I don't believe windows likes this very much.

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