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Sender always is null(Invalid Signal signature: textMessageReceived(str))

  • OS : win10 64bits
    python : 3.7.3(anaconda)
    install by pip : pip install PySide2(PySide2 5.12.2)
    llvm: libclang-release_70-based-windows-mingw_64\libclang

    I am trying to find out the sender(find out which QWebSocket send the message), but it always tell me the sender is None, try to follow the suggestion in this post, use different way to connect signal and slot, but it always give me error message "Invalid Signal signature: textMessageReceived(str)".

    Minimum codes to reproduce:

    import sys
    from PySide2.QtCore import Slot, SIGNAL
    from PySide2.QtNetwork import QHostAddress
    from PySide2.QtWidgets import QApplication, QPushButton
    from PySide2.QtWebSockets import QWebSocketServer, QWebSocket
    class Worker(QPushButton):
        def __init__(self):
            super(Worker, self).__init__()
            self.__server = QWebSocketServer("sss", QWebSocketServer.NonSecureMode)
            if self.__server.listen(QHostAddress.AnyIPv4, 1234):
                print("server listening")
            self.__socket = QWebSocket()
            print("socket open")
        def __connect(self):
        def __clientConnected(self):
            print("client connected sender:", self.sender())  # this sender is not null
            clientConnected = self.__server.nextPendingConnection()
            # connect by this solutoin, the sender always is null
            # connect by SIGNAL always tell me Invalid Signal signature: textMessageReceived(str)
            clientConnected.connect(clientConnected, SIGNAL("textMessageReceived(str)"), self.__textMessageReceived)
        def run(self):
            print("run sender:", self.sender())  # this sender is not null
            self.__socket.sendTextMessage("send message")
        def __textMessageReceived(self, msg):  # this sender always is null
            print("text message sender:", self.sender())
    if __name__ == "__main__":
        app = QApplication(sys.argv)
        worker = Worker()
        worker.setText("click me")
        worker.resize(640, 480)

    I try to import QString, but cannot do it
    Do anyone know how to solve it?Thanks

  • I think you are trying to be too slick, implementing network code under a pushbutton. Separate out the functionality into different objects and communicate between them when necessary.

  • @Kent-Dorfman Thanks, this is just a minimum example to show the issues, do you know how could I solve the issue of "Sender is None"? Thanks

  • Remove the @Slot(), I had the same question, and I remove the @Slot(), everything is ok.

  • Banned

    Okay removing @Slot() means you are not using Signal/Slots and will be making a direct function call. The question I pose is what are you trying to implement with your version of this as I realize this is just an MRE of problem you are experiencing.

    As a reference without seeing the rest I am going to guess you might be confusing things. Sockets are different than Signal/Slots as Sockets are mainly for internet communication and Signal/Slots are for internal code communication mainly between Threads. So are you attempting internet communication or internal (to the application) code communication?

    If the latter then I can help you sort out how to properly use Signal/Slots if the former I will have to pass as I have not delved into Sockets yet.

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