Home
FAQ Home
How can I convert a QString to char* and vice versa?

Sorted by Category:

Organized by tag:

How can I convert a QString to char* and vice versa?

In order to convert a QString [doc.qt.nokia.com] to a char*, then you first need to get a local8Bit representation of the string by calling toLocal8Bit() [qt.nokia.com] on it which will return a QByteArray [doc.qt.nokia.com]. Then call data() [qt.nokia.com] on the QByteArray to get a pointer to the data stored in the byte array.

See the following example for a demonstration:

int main(int argc, char **argv)
{
QApplication app(argc, argv);
QString str1 = "Test";
QByteArray ba = str1.toLocal8Bit();
const char *c_str2 = ba.data();
printf("str2: %s", c_str2);
return app.exec();
}

Note that it is necessary to store the bytearray before you call data() on it, a call like the following

const char *c_str2 = str2.toLocal8Bit().data();

will make the application crash as the QByteArray has not been stored and hence no longer exists

To convert a char* to a QString you can use the QString constructor that takes a QLatin1String [doc.qt.nokia.com] to ensure the locale encoded string is correct with fromLocal8Bit() [qt.nokia.com], e.g:

QString string = QString(QLatin1String(c_str2));
QString string = QString::fromLocal8Bit(c_str2);

In addition, if you want to just print out the string then you can use qPrintable() [qt.nokia.com] as a quick means to do this without having to convert to a char *. For example:

printf("str2: %s", qPrintable(str1));

3 comments

April 29, 2011

dialingo

Robot Herder

Conversion of QString to char* depends on the encoding. In most cases UTF-8 is the right choice.
Therefore:

QString qString1 = “hello”;
const char *cString = qString1.toUtf8().constData();
QString qString2 = QString::fromUtf8(cString);

April 29, 2011

dialingo

Robot Herder

The post above contains a memory leak. Here is the corrected version:

QString qString1 = "hello";
QByteArray byteArray = qString1.toUtf8();
const char* cString = byteArray.constData();
QString qString2 = QString::fromUtf8(cString);

May 2, 2011

AndyS

Lab Rat

I removed the comments pertaining to the original state of the FAQ and have now updated it to show toLocal8Bit() usage instead and added a note about qPrintable() too.

Tags what is this? Undo?

Ratings what is this?

Qt DevNet Blog

Qt Developer Network is moving to the Qt Project

Qt 4.8 Docs now on Qt DevNet

Qt Developer Network Forums are Buzzing

Not registered?

How can I convert a QString to char* and vice versa?

3 comments

April 29, 2011

April 29, 2011

May 2, 2011

Write a comment