Does Qt Remote Objects can only connect signal and slot defined by sub class?

Mozzie

Hi,

Recently, I am using Qt Remote Objects, I want to implement different server with same API, so I write a base class which defined some signal and slots, and then implement it in the server application.
for example:

class A : public QObject {
    Q_OBJECT
signals:
	void testSignal();

public slots:
	void parentSlot() {}
	virtual void testSlot() = 0;

}

class B : public A {
	Q_OBJECT

public slots:
	virtual void testSlot() override {
            emit testSignal();
	}
}

B* server = new B(this);
host->enableRemoting(server, m_serverName)

I found I can connect testSlot but I can not connect testSignal and parentSlot from client.

such as:


auto interface = node->acquireDynamic(m_serverName);
qDebug() << "interface" << interface;
if (interface) {
	connect(interface, &QRemoteObjectDynamicReplica::initialized, this, [this, interface](){
		connect(this, SIGNAL(testSlotReady()), interface, SLOT(testSlot()));
		connect(this, SIGNAL(testSlotReady()), interface, SLOT(parentSlot()));
		connect(interface, SIGNAL(testSignal()), interface, SLOT(onTestSignal()));
		
	});
	connect(interface, &QRemoteObjectDynamicReplica::stateChanged,
			this, [this](QRemoteObjectReplica::State state, QRemoteObjectReplica::State oldState){
		qDebug() << "state" << state << oldState;
	});


}

It said: QObject::connect: No such slot ... and QObject::connect: No such signal ... when the application is running.
Does Qt Remote Objects can only connect signal and slot defined by sub class? Why or is there any thing I'm using is not correct?

Thank you.

jsulm

@Mozzie said in Does Qt Remote Objects can only connect signal and slot defined by sub class?:

but I can not connect testSignal and parentSlot from client

Where in the code you posted are you connecting them?
And what happens if you try to do so?

Mozzie

@jsulm
Hi,
I am using dynamic replica of the Qt Remote Objects, the conncting code is

	connect(interface, &QRemoteObjectDynamicReplica::initialized, this, [this, interface](){
		connect(this, SIGNAL(testSlotReady()), interface, SLOT(testSlot()));
		connect(this, SIGNAL(testSlotReady()), interface, SLOT(parentSlot()));
		connect(interface, SIGNAL(testSignal()), interface, SLOT(onTestSignal()));
		
	});

It said: QObject::connect: No such slot ::parentSlot and QObject::connect: No such signal ::testSignal when the application is running.
the connect(this, SIGNAL(testSlotReady()), interface, SLOT(testSlot())); is working, but the other two is not working unless I move parentSlot from class A to Class B, then the connect(this, SIGNAL(testSlotReady()), interface, SLOT(parentSlot())); will work.

KroMignon

@Mozzie said in Does Qt Remote Objects can only connect signal and slot defined by sub class?:

Recently, I am using Qt Remote Objects, I want to implement different server with same API, so I write a base class which defined some signal and slots, and then implement it in the server application.

I don't know if you post the complet header code, if so, then please add Q_OBJECT to the class definition!

class A : public QObject {
    Q_OBJECT
...
};

class B : public A {
    Q_OBJECT
...
};

Q_OBJECT is mandatory is you want to add signals/slots to a class (cf. https://doc.qt.io/qt-5/qobject.html#details or )

Mozzie

@KroMignon

Thank you. I did not post the complet header code, it is just a simplify version of my code, this might not be the reason.

jsulm

@Mozzie Please try with Qt5 connect syntax:

connect(interface, &BASE_CLASS::testSignal, interface, &INTERFACE_CLASS::onTestSignal);

You should not use the old connect syntax anymore.

Mozzie

@jsulm

When use acquireDynamic, It means I dont have the interface header file in the server application, I only know the signals and slots of it, and the QRemoteObjectDynamicReplica *QRemoteObjectNode::acquireDynamic(const QString &name) function return a replica, so I can not use Qt5 connect syntax. and the child slot is working, so I think this migth not be a problem.

mattmart3

Hi everyone, any news on this?

I am experiencing the same issue running PyQt5. Following a simple sever-client example (simplified version of this example):

Server app:

from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from PyQt5.QtRemoteObjects import *


class Person(QObject):
    sig_name = pyqtSignal(str)

    def __init__(self):
        super().__init__()


class Name(Person):
    def __init__(self):
        super().__init__()
        self.startTimer(1000)

    def timerEvent(self, event):
        self.sig_name.emit("Test name")


class Server(QObject):
    def __init__(self):
        super().__init__()
        self.name = Name()
        host = QRemoteObjectHost(QUrl("local:server"), self)
        host.enableRemoting(self.name, "name")


app = QCoreApplication([])
s = Server()
app.exec()

Client app:

from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from PyQt5.QtRemoteObjects import *


class Client(QObject):
    def __init__(self):
        super().__init__()
        node = QRemoteObjectNode(self)
        node.connectToNode(QUrl("local:server"))

        self.remote_name = node.acquireDynamic("name")
        self.remote_name.initialized.connect(self.onInitName)

    def onInitName(self):
        self.remote_name.sig_name.connect(self.print_info)

    def print_info(self, x):
        print("-->:", x)


app = QCoreApplication([])
c = Client()
app.exec()

Since the sig_name signal is defined in the super class of the Name class, the client fails on connection:

    self.remote_name.sig_name.connect(self.print_info)
    ^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'QRemoteObjectDynamicReplica' object has no attribute 'sig_name'

If the signal is instead defined in the Name class it works fine:

class Person(QObject):
    sig_name_super = pyqtSignal(str)

    def __init__(self):
        super().__init__()


class Name(Person):
    sig_name = pyqtSignal(str)

    def __init__(self):
        super().__init__()
        self.startTimer(1000)
        self.sig_name_super.connect(self.sig_name)