Wait until slot end to continue program execution

Babs

Hello, I'm working on a CanBus API. I 'm storing received data from my device in a QStringList. There i connect the signal QCanBusBusFrame::Received frame to a slot processFrame.
The problem is when i read the QStringList in my main function it is empty. Seconds after it is filled.
Here is my connection and code:

void DevicesManagement::processReceivedFrames()
{
    if(!m_device)
        return;
    while (m_device->framesAvailable()) {
        const QCanBusFrame frame = m_device->readFrame();
        m_receivedFrames.append(frame.payload().toHex());
        set_deviceProfile(frame.payload().toHex().right(8).toUpper());
    }
    emit processOver();
    qDebug()<<get_deviceProfile();
    disconnect();
}

And i connected my slot to the signal like this:

    connect(m_device, &QCanBusDevice::framesReceived, this, &DevicesManagement::processReceivedFrames);

And there is my main

int main (int argc, char * argv []) {
    QGuiApplication app (argc, argv);
    QQmlApplicationEngine engine (&app);
    registerQtQmlTricksUiElements (&engine);
    registerQtQmlTricksSmartDataModel (&engine);
    DevicesManagement *manager=new DevicesManagement(&engine);
    QList<QObject*>mDeviceList;
    manager->initializeDevices("125000");
    manager->deviceProfileProcess();
    qDebug()<<manager->get_deviceProfile();
 

    engine.load (QUrl ("qrc:///splash_power.qml"));

    return app.exec ();
}

The problem is that my slot processReceivedFrames is not over yet when i read my frame. Therefore it is empty.
Anyone got an idea to solve that issue?

jsulm

@Babs said in Wait until slot end to continue program execution:

qDebug()<<manager->get_deviceProfile();

Do you mean it is empty here?

Babs

@jsulm yes and it is filled when my slot ends

jsulm

@Babs But why do you need to read it there?
Correct way would be to emit a signal from DevicesManagement when the list is complete and read it in the slot.

Babs

@jsulm I use it to create an Object that i will expose to qml

Babs

@Babs here is what i do next in my main

int main (int argc, char * argv []) {
    QGuiApplication app (argc, argv);
    QQmlApplicationEngine engine (&app);
    registerQtQmlTricksUiElements (&engine);
    registerQtQmlTricksSmartDataModel (&engine);
    DevicesManagement *manager=new DevicesManagement(&engine);
    QList<QObject*>mDeviceList;
    manager->initializeDevices("125000");
    manager->deviceProfileProcess();
    qDebug()<<manager->get_deviceProfile();
    CanOpenDevice *dev1=new CanOpenDevice(23,manager->get_deviceProfile(),&engine);
    mDeviceList.append(dev1);
    qmlRegisterType<CanOpenDevice>("com.device",1,0,"CanDevice");
    engine.rootContext()->setContextProperty("mManager",manager);
    engine.rootContext()->setContextProperty("mModel",QVariant::fromValue(mDeviceList));


    engine.load (QUrl ("qrc:///splash_power.qml"));

    return app.exec ();
}

jsulm

@Babs You're trying to program synchronously using an asynchronous framework. You really should do it in an asynchronous way. Using signals/slots. Connect a slot in CanOpenDevice to a signal in DevicesManagement which is emitted when the list is filled.

Babs

@jsulm thank you i'll try to do so. I thought i could may be suspend my main thread until my variable is filled

J.Hilk

@Babs

lambdas are your friend ;-)

QObject::connect(manager, &DevicesManagement::devicesReady, &engine, [&engine, & mDeviceList](QStringList list)->void{
      qDebug()<< list;
    CanOpenDevice *dev1=new CanOpenDevice(23, list,&engine);
    mDeviceList.append(dev1);
    engine.rootContext()->setContextProperty("mManager",manager);
    engine.rootContext()->setContextProperty("mModel",QVariant::fromValue(mDeviceList));     
});
engine.load (QUrl ("qrc:///splash_power.qml"));

    return app.exec ();

should work, fine.

But it's untested.

Babs

@J.Hilk Thanks you. Its works.
Regards.