From C++ consume QML signal (Qt5/Qml2)

[A Former User]

Hello

I'm just at the beginning of learning C++/Qt and i stumble over some basics.

My Qml file exposes a signal stoppedSignal(string msg). I would like to consume this signal from within c++, but i get strange errors instead.

Errors:
in function 'Blubb:Blubb()':
undefined reference to 'vtable for Blubb'
in function 'Blubb::~Blubb()':
undefined reference to 'vtable for Blubb'

I've tried several ways and this is the most current, which is a rewrite of a tutorial actually. I would like to use the "new way" of connecting signals, but there seems to be no way of getting an actual function pointer to a qml signal.

So whats wrong here?

[code]import QtQuick 2.0
import QtQuick.Window 2.0
import QtMultimedia 5.0

Window {
id: mainWindow
width: 100
height: 62

property string thefile: "/home/sfuser/Downloads/video1.mp4"
signal stoppedSignal(string msg)

Rectangle {
id: rec
anchors.fill: parent

Video {
  id: videoPlayer
  anchors.fill: parent
  source: mainWindow.thefile
  focus:  true
  autoPlay: true
  onStopped: mainWindow.stoppedSignal("videoX");
}

}
}[/code]
[code]#include <QtGui/QGuiApplication>
#include <QtQuick/QQuickView>
#include <QQmlProperty>
#include <QQmlEngine>
#include <QQmlComponent>
#include <QQuickItem>
#include <QDebug>
#include <QObject>
#include <QString>
#include "qtquick2applicationviewer.h"

class Blubb : public QObject{
Q_OBJECT

public slots:
void hasStopped(const QString &msg){
qDebug() << "Video has stopped! " << msg;
}
};

int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);

QQmlEngine engine;
QQmlComponent component(&engine, QUrl("qml/interaction2/Video.qml"));
QObject *object = component.create();

QQuickWindow *item = qobject_cast<QQuickWindow*>(object);
item->setHeight(300);
item->setWidth(600);
//item->setProperty("theurl", "http://www.youtube.de");

Blubb blubb;
QObject::connect(item, SIGNAL(stoppedSignal(QString)), &blubb, SLOT(hasStopped(QString)));

return app.exec();

}[/code]

[A Former User]

I recreated the Blubb class with QtCreator. The result was this code which looks nearly the same as mine. But not completly.

Can anyone explain to me what happened?

[code]#ifndef BLUBB_H
#define BLUBB_H

#include <QObject>
#include <QDebug>

class Blubb : public QObject
{
Q_OBJECT
public:
explicit Blubb(QObject *parent = 0);

signals:

public slots:
void hasStopped() {
qDebug() << "Video has stopped!";
}
};

#endif // BLUBB_H
[/code]

[A Former User]

yes, constructor is missing in your code.

[A Former User]

[quote author="Serenity" date="1365576471"]yes, constructor is missing in your code.
[/quote]

I had at some point something like this:
[code]
public:
Blubb();
~Blubb():
[/code]

This did not help. The Parameter the constructor is expecting is mandatory for QObjects i presume, which would explain the error.

Is the syntax
[Code]
QObject *parent = 0 [/code]

A default initialization of the parameter in case nothing is provided otherwise?