By default, you can not throw exceptions from signals and slots, and if you try it, you get the following message:
Qt has caught an exception thrown from an event handler. Throwing exceptions from an event handler is not supported in Qt. You must reimplement QApplication::notify() and catch all exceptions there.
So, what to do? The answer is simple: Overwrite the function bool
QApplication::notify(QObject * receiver, QEvent * event) so that it
catches all thrown exceptions. Here is some sample code:
#include <QtGui>
#include <QApplication>
class MyApplication : public QApplication {
public:
MyApplication(int& argc, char ** argv) :
QApplication(argc, argv) { }
virtual ~MyApplication() { }
// reimplemented from QApplication so we can throw exceptions in slots
virtual bool notify(QObject * receiver, QEvent * event) {
try {
return QApplication::notify(receiver, event);
} catch(std::exception& e) {
qCritical() << "Exception thrown:" << e.what();
}
return false;
}
};
int main(int argc, char* argv[]) {
MyApplication app(argc, argv);
// ...
}
Of course, you can also inherit from QCoreApplication to get rid of
the QtGui dependency, or display a nice dialog box instead of printing
the messages to the console, or…