Question

I have an MFC source file that I need to compile under Qt. This file uses MFC/ATL CString. Specifically it uses a CString as an argument to iostream::open(). I have written a CString class that inherits from QString so that I can use most of QStrings’ functionality.

My main concern is that I cannot get my CString implementation to work where iostream::open() is called:

Here is a bit of my class declaration:

    class CString : public QString {
    public:
        CString() : QString() {}
        CString(const QString& other) : QString(other) {}
        CString(const CString& other) : QString(other) {}
        CString(_In_opt_z_ const XCHAR* pszSrc) : QString( pszSrc ) { *this = pszSrc; }
        CString(const char* pszSrc) : QString( pszSrc ) {}
        ...
    }

And, here is a portion of code to use the CString:

ofstream outfile;
CString Path("dump.txt");

outfile.open(Path);

The error is:

no matching function for call to ‘std::basic_ofstream >::open(CString&)’

Under ‘normal’ circumstances, I would simply do something like:

outfile.open(Path.toStdString().c_str());

However, that is not an option. No modification of the original code is authorized. 🙁

Is there a way to do this, or am I going to have to rebuild the class using the same, rather more complex and lengthy code, that Microsoft uses in cstringt.h?

Thanks

Answer 1

Define a typecast operator for your CString class as follows:

operator const char*() { return this->toStdString().c_str(); }