How to convert QString to std::string?

Question

You can use:

QString qs;
// do things
std::cout << qs.toStdString() << std::endl;

It internally uses QString::toUtf8() function to create std::string, so it's Unicode safe as well. Here's reference documentation for QString.

One of the things you should remember when converting QString to std::string is the fact that QString is UTF-16 encoded while std::string... May have any encodings.

So the best would be either:

QString qs;

// Either this if you use UTF-8 anywhere
std::string utf8_text = qs.toUtf8().constData();

// or this if you're on Windows :-)
std::string current_locale_text = qs.toLocal8Bit().constData();

The suggested (accepted) method may work if you specify codec.

See: http://doc.qt.io/qt-5/qstring.html#toLatin1

If your ultimate aim is to get debugging messages to the console, you can use qDebug().

You can use like,

qDebug()<<string; which will print the contents to the console.

This way is better than converting it into std::string just for the sake of debugging messages.

QString qstr;
std::string str = qstr.toStdString();

However, if you're using Qt:

QTextStream out(stdout);
out << qstr;

Best thing to do would be to overload operator<< yourself, so that QString can be passed as a type to any library expecting an output-able type.

std::ostream& operator<<(std::ostream& str, const QString& string) {
    return str << string.toStdString();
}

An alternative to the proposed:

QString qs;
std::string current_locale_text = qs.toLocal8Bit().constData();

could be:

QString qs;
std::string current_locale_text = qPrintable(qs);

See qPrintable documentation, a macro delivering a const char * from QtGlobal.