UPDATE:
This is the overload of the QObject::connect call that you are trying to refer to, and what your error is says it can't find based on the parameters you give it:
http://doc-snapshot.qt-project.org/qdoc/qobject.html#connect-5
QMetaObject::Connection QObject::connect(
const QObject * sender,
PointerToMemberFunction signal,
Functor functor) [static]
You have in your parameter assignments:
const QObject * sender = &exitApplicationAction
The above passes as the correct parameter, but as soon as you leave your current scope it will become a bad pointer, and cause a runtime crash. Instead, allocate onto the heap, and use parenting correctly. But this doesn't work with your other parameters you give it... read on.
PointerToMemberFunction signal = &QSystemTrayIcon::activated
Your QObject * sender is not a QSystemTrayIcon, it is a QAction *. Therefore it is not a valid signal to connect to. If you want to connect to the activation signal of the QSystemTrayIcon, you have to pass the QSystemTrayIcon pointer as the first parameter.
Functor functor = [&](QSystemTrayIcon::ActivationReason activationReason) { qApp->quit();}
This functor looks like it could work. Double check the lambda examples if it doesn't seem to work.
End of UPDATE.
This relates to the new lambda syntax supported in Qt 5, and if your compiler supports it.
New: connecting to simple function
The new syntax can even connect to functions, not just QObjects:
connect(sender, &Sender::valueChanged, someFunction);
pro
can be used with tr1::bind
can be used with c++11 lambda expressions
connect(sender, &Sender::valueChanged,
tr1::bind(receiver, &Receiver::updateValue, "senderValue", tr1::placeholder::_1) );
connect(sender, &Sender::valueChanged, [=](const QString &newValue) {
receiver->updateValue("senderValue", newValue);
} );
cons
There is no automatic disconnection when the ‘receiver’ is destroyed
On the wiki page it gives a few examples of how to use the lambda functionality:
http://qt-project.org/wiki/New_Signal_Slot_Syntax
http://qt-project.org/wiki/New_Signal_Slot_Syntax#45f5369b0d8445adbaf54cd74a36b823
And if you check out MSDN there is quite a bit on the Lambda syntax:
http://msdn.microsoft.com/en-us/library/dd293603.aspx
It gets a little complex with all the supported options of c++, return values, scoping of variables, variable references, etc. So for now finding an example that is close should work.
But like was said in the comments above, there is probably a better way to do this.
Instead instantiate the QAction as a pointer inside your main widget or QMainWindow, and connect it to the close event slot of that window. Like so:
// somewhere in your constructor
QAction * action = new QAction("Quit", this);
QObject::connect(action, SIGNAL(triggered()), this, SLOT(close()));
// And make sure you add the action to a menu or a button or a toolbar, too
Hope that helps.
