Problem with C++ signal to QML

jech

Hi,

I know there is plenty of documentation on this but since I'm a C++ beginner, some of the constructions don't make much sense to me. Also almost everybody is searching for the opposite direction - QML signal to C++. There is not much written about propagating signals from C++ to QML.

Anyway I found his "guide":http://developer.nokia.com/Community/Wiki/Connecting_Qt_signal_to_QML_function and I based my code on it. Here is what I created:

mediascan.h

@#ifndef MEDIASCAN_H
#define MEDIASCAN_H
#include "filesearch.h"
#include "mediatag.h"
#include <QDebug>

#include <QObject>

class MediaScan : public QObject
{
Q_OBJECT

public:
explicit MediaScan(QObject *parent = 0);
Q_INVOKABLE void scan(const QStringList &directories);

signals:
void fileCountUpdate(int &fileCount);
void filesFound();
void progress(int &progress);
void filesScanned(QList<QStringList> &mediaTags);

public slots:
void onFileCountUpdate(const int &progress);
void onProgress(const int &progress);
void onFilesFound(const QStringList &fileList);
};

#endif // MEDIASCAN_H
@

main.cpp

@#include <QtGui/QGuiApplication>
#include <QQmlContext>
#include "qtquick2applicationviewer.h"
#include "mediascan.h"

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

QtQuick2ApplicationViewer viewer;
viewer.setMainQmlFile&#40;QStringLiteral("qml/Muzika/main.qml"&#41;&#41;;
viewer.showExpanded();
QQmlContext* ctxt = viewer.rootContext();
MediaScan* mediascan = new MediaScan();
ctxt->setContextProperty("mediascan", mediascan);
QQuickItem *rootObject = viewer.rootObject();
QObject::connect(&mediascan, SIGNAL(filesFound()), rootObject, SLOT(filesFound()));
return app.exec&#40;&#41;;

}
@

What the code does is that it gets some paths from QML UI and runs the scan function. Then I create a new thread which searches for media files in the directories and returns back some information (signals) about the progress. I think that what is inside mediascan.cpp is not important.

What happens when I try to compile the code is that I get following error:
@C:\Qt\projects\Muzika\main.cpp:18: note: candidate expects 3 arguments, 4 provided
QObject::connect(&mediascan, SIGNAL(filesFound()), rootObject, SLOT(filesFound()));
^@

This absolutely doesn't make sense to me. In all references I found the connect function needs 4 arguments. What is wrong in my code? And is this the right way to connect signals with QML UI?

p3c0

Hi,

@
QObject::connect(&mediascan, SIGNAL(filesFound()), rootObject, SLOT(filesFound()));
@
NO need to pass the address (&mediascan) here. It expects a pointer.
So just

@
QObject::connect(mediascan, SIGNAL(filesFound()), rootObject, SLOT(filesFound()));
@
should work

jech

Thanks for the tip. After some more tweaking I finally made it work.