class Settings : public QObject
{
    Q_OBJECT
    Q_PROPERTY(bool value READ getValue WRITE setValue NOTIFY valueChanged)
public:
    explicit Settings(QObject *parent = 0);
    bool getValue() {return this->value;}
    void setValue(bool val) {this->value = val; emit valueChanged(val);}
private:
    bool value;
signals:
    void valueChanged(bool);
};


// In main method:
Settings* settings = new Settings();
view->rootContext()->setContextProperty("settings", settings);

// In QML:
Switch {
    checked: settings.value
    //if using the following it is working but warning about a binding loop:
    //onCheckedChanged: settings.value = checked
}