Custom QEvent for QStateMachine : type recognition won't work

tomviow

Hello everyone,
I have a problem I've been struggling with for a few hours now. I have a QStateMachine controlling a GUI and its screens, and I wanna link this SM to the socket for a TCP/IP communication my software needs.

Therefore, my aim is to post a custom event (ConnectionEvent) to the state machine (GUIStateMachine) in order to process a custom transition (ConnectionTransition). I followed the example of the documentation (https://doc.qt.io/qtforpython/overviews/statemachine-api.html#events-transitions-and-guards)

The problem is, once I post the event from my connection-related class, the eventTest method from ConnectionTransition is unable to get the type of my custom event (defined to QEvent.User + 2). It returns PySide2.QtCore.QEvent.Type.None_.

If you have any advice, would be very appreciated ! Thank you

Here are my custom types :

class ConnectionEvent(QEvent):

    def __init__(self, connected):
        print("ConnectionEvent")
        super(ConnectionEvent, self).__init__(QEvent.Type(QEvent.User + 2))
        self.setAccepted(connected)


class ConnectTransition(QAbstractTransition):

    def __init__(self, connected):
        super(ConnectTransition, self).__init__()
        self.state = connected

    def eventTest(self, event) -> bool:
        if event.type() != QEvent.Type(QEvent.User + 2):
            print("Unrecognized type")
            print(event.type()) #there I get PySide2.QtCore.QEvent.Type.None_
            return False
        else:
            print("Recognized type")
            return self.state == event.isAccepted()

The code defining my transitions in GUIStateMachine:

 t1 = ConnectTransition(True)
 t1.setTargetState(self.states["CONNECTED"])
self.states["WAITING"].addTransition(t1)

t2 = ConnectTransition(False)
t2.setTargetState(self.states["CONNECTION"])
self.states["CONNECTED"].addTransition(t2)

And finally the code posting the event :

def setConnected(self, value):
        # some code
    
        print("posting event")
        event = sm.ConnectionEvent(value)
        sm.GUIStateMachine.getInstance().postEvent(event)

tomviow

@Denni-0 said in Custom QEvent for QStateMachine : type recognition won't work:

View

Thank you for your answer.
I see your point : I'll have to implement an intermediary controller class between my socket (pure python) and my QStateMachine. To be fair, I'm still at the step of creating/conceiving the code, and I was planning on doing this next.

However, the thing that worries me is that I'm not able to retrieve the data I want from my custom QEvent. It's supposed to be working in C++ but I don't know if there is a specificity about Python that I'm missing, concerning "abstract classes method parameters" (here, event from eventTest method which is QEvent) and "inherited classes method arguments" (here, my ConnectionEvent that I post to the SM). It's hard to be clear but I hope you (or someone maybe?) get my point.

SGaist

Hi and welcome to devnet,

Do you have a singleton instance of your state machine ?

tomviow

@SGaist I do have a singleton instance of my state machine.

@Denni-0 I completely agree with you. I'll work around a controller which will be the intermediary layer between my components.

Eventually, I found out how to link my socket to my GUI: I just created a "smart boolean" class (QObject), from which I emit signals when the value changes from false to true, or from true to false. With these signals, I can proceed to the transitions and actions I want.