Is there any difference between QRegularExpression and QRegExp?

Question

I see there is a new class for regular expressions - QRegularExpression. Is it just a typedef for QRegExp, or a new class, or what? And why do we need it, we al

Answer 1

At least for Qt 4.8. I can give a very practical reason to use QRegularExpressions instead of QRegExp:

Do these look dangerous to you?

int index = myQString.indexOf(myQRegExp);
bool okay = myQString.contains(myQRegExp);

Both lines can corrupt your heap, crash or hang your application. I experienced heap corruption and hang with Qt 4.8. The blog post QString::indexOf() versus Qt 4.5 explains that QString::indexOf() modifies a const QRegExp object. QString::contains() inlines QString::indexOf() so it's the same problem.

If you're stuck with Qt4 and thus QRegExp, you could use

int index = myQRegExp.indexIn(myQString);
bool okay = (myQRegExp.indexIn(myQString) != -1); 

in your sources instead. Or patch the Qt Sources.