the QNetworkAccessManager::authenticationRequired signal expects the connected slots to fill in the QAuthenticator object (and notice that it doesn't work with queued connections).

This is currently being used in some places inside Qt, f.i. Now, you already can abuse (a little bit) of this infrastructure, for instance by emitting a signal which carries a pointer and let the slots modify the pointee. Therefore, you just don't care about the receivers: you emit the signal and move on.

At signal emission time, any number of receivers can be connected to that signal (0, 1, N). The emitter is completely decoupled from any connected receivers, and in fact, it knows nothing about them. It's not a matter of being technically impossible it simply does not make sense imho.Ī signal is emitted from a 'component' when it changes in some way that may be interesting for other components. Sorry if I talk about something impossible. Probably this was discussed thousands of times but I didn't read all Qt disputes. But isn't that possible just think about some extension of signal/slot system? To let receive returned values more graciously. Especially when receiver and sender are from different plugins. I always used 'duplex' connections to get response from QObject when needed.

Qt returning a value from a slot