Can't use a c++ signal in QML

JorgeCosta87

I have tried to receive a signal from a c++ class to QML, without any success. I have followed the tutorial provided by QT
[http://doc.qt.io/qt-5/qtqml-cppintegration-exposecppattributes.html](link url).

My code:
The main class (c++)
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);

Manager manager;
QQmlApplicationEngine engine;

qmlRegisterType<Manager>("costa.manager", 1, 0, "Manager");

engine.rootContext()->setContextProperty("manager",&manager);
engine.load(QUrl(QLatin1String("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
    return -1;

return app.exec();

}

Class Manager .h with the signal:

class Manager : public QObject
{
Q_OBJECT

public:
explicit Manager(QObject *parent = nullptr);

signals:
void isVechicleConnected(const bool &b);

...
}

Class Manager .cpp

void Manager::isConnected(const bool &b)
{
qDebug() << "signal"; //to check if i'm sendding the signal
emit isVechicleConnected(b);
}

QML main:

import QtQuick 2.7
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.3
import QtQuick.Controls.Material 2.0
import costa.manager 1.0

ApplicationWindow {

...
Manager{
onIsVechicleConnected: {
console.log("Connected!!!" + b)
}
}
...
}

How to fix it ?

thanks !

Eeli K

@JorgeCosta87 Now you create a new object of type Manager in main.qml. Remove that. You don't need to register the type. Instead, the object named 'manager' is a context property and is globally available in your QML code. You need to use Connections to catch the signal:

Connections: {
target: manager
onIsVehicleConnected: {}
}

BTW, the signal is weirdly named. E.g. QGamepad has the "connected" property and "connectedChanged" signal, and "onConnectedChanged" would be the event handler in QML. "isConnected", judged by its name, should be a query method which doesn't send a signal. I recommend making "connected" a real property. I have something like this in a project:

...
Q_OBJECT
Q_PROPERTY(bool connectedStatus MEMBER m_connected NOTIFY connectedStatusChanged)
...
private: bool m_connected;
...
signals: void connectedStatusChanged(bool connected);

JorgeCosta87

@Eeli-K said in Can't use a c++ signal in QML:

onConnectedChanged

Thanks a lot!
True, makes much more sense that name.