How to Convert Qstring to Std: :String?

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.

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.

The simplest way would be QString::toStdString().

You can use this;

QString data;
data.toStdString().c_str();

There is also the option to use qPrintable or qUtf8Printable

E.g.:

#include <QString>
#include <iostream>

int main()
{
    QString myString = "Hello World";

    // Using qPrintable
    std::cout << "qPrintable: " << qPrintable(myString) << std::endl;

    // Using qUtf8Printable
    std::cout << "qUtf8Printable: " << qUtf8Printable(myString) << std::endl;

    return 0;
}

 QString data;
   data.toStdString().c_str();

could even throw exception on VS2017 compiler in xstring

 ~basic_string() _NOEXCEPT
        {   // destroy the string
        _Tidy_deallocate();
        }

the right way ( secure - no exception) is how is explained above from Artyom

 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();

HA~I finally find the answer which I can run! Share to you now~

QString qStr = "Hello world";
QByteArray qByteArray = qStr.toUtf8();
char* cStr = qByteArray.data();
const char* test = cStr;
qDebug()<<test<<endl;

Try this:

#include <QDebug>
QString string;
// do things...
qDebug() << "right" << string << std::endl;