QObject::connect: signal not found in promoted widget with Lambda syntax

[JKSH]

Quick test: Create a dummy class that inherits QObject (not a promoted QWidget!) and also give it a signal void deleteRequest(QVector<int> uids). Instantiate this dummy class and try to connect this dummy signal to your lambda.

Does it work?

[Taz742]

Guys... I dont know why but my CustomTreeWidget class have a UI. Should it be? :D

[jsulm]

@Taz742 said in QObject::connect: signal not found in promoted widget with Lambda syntax:

I dont know why but my CustomTreeWidget class have a UI

What do you mean? It is a GUI class, so it has a UI. Or do you mean it has ui member variable?

[J.Hilk]

Hi,
have you registered QVector as a metatype - using qRegisterMetaType, to use it via Signal/Slots?

[Taz742]

@J.Hilk
In main.cpp

    qRegisterMetaType<QVector<int>>("QVector<int>");

Now i am tryng but have a same situation.

[SGaist]

Hi,

here's a dummy example:

#include <QtCore>
#include <QtDebug>

class MyClass : public QObject
{
    Q_OBJECT

signals:
    void deleteRequest(QVector<int> uids);
    void done();

public slots:
    void trigger()
    {
        emit deleteRequest(QVector<int>{1, 2, 3, 4});
        QTimer::singleShot(1000, this, &MyClass::done);
    }
};

int main(int argc, char** argv)
{
    QCoreApplication app(argc, argv);

    MyClass mc;
    QTimer::singleShot(1000, &mc, &MyClass::trigger);
    QObject::connect(&mc, &MyClass::done, qApp, &QCoreApplication::quit);
    QObject::connect(&mc, &MyClass::deleteRequest, [](const QVector<int>& data) { qDebug() << data; });
    return app.exec();
}

#include "main.moc"

The content of the QVector is printed after one second and the application ends after another one. Does it work on your machine ?

[Taz742]

@SGaist
Yes its work. I am also tryed to create new project, move my CustomTreeWidget and work there.

[Taz742]

@SGaist
I have a same situation in other class.
Can you check this example?

#ifndef IMAGEWORKER_H
#define IMAGEWORKER_H

#include <QObject>
#include "QDebug"
#include "globalhelper.h"
#include "QThread"
#include "QMutex"
#include "QFile"
#include "QDir"
#include "QCryptographicHash"
#include "QByteArray"

class ImageWorker : public QObject
{
    Q_OBJECT
public:
    explicit ImageWorker(QObject *parent = 0) {
        Q_UNUSED(parent);
        QThread *thread = new QThread;
        this->moveToThread(thread);
        connect(thread, &QThread::started, this, &ImageWorker::doWork);
        connect(this, &ImageWorker::finished, thread, &QThread::quit);
        connect(this, &ImageWorker::finished, this, &ImageWorker::deleteLater);
        connect(thread, &QThread::finished, thread, &QThread::deleteLater);
        thread->start();
    }

    ~ImageWorker() {
        qDebug() << "ImageWorker deleted";
    }

signals:
    void finished();

public slots:
    void doWork() {
        emit finished();
    }

private:
    bool compareImages(const QByteArray &myImage, const QByteArray &serverImage) const
    {
        return myImage.toHex() == serverImage.toHex();
    }

    QByteArray fileChecksum(const QByteArray &bytes, QCryptographicHash::Algorithm hashAlgorithm = QCryptographicHash::Md5) const
    {
        QCryptographicHash hash(hashAlgorithm);
        hash.addData(bytes);
        return hash.result();
    }

};


#endif // IMAGEWORKER_H

[SGaist]

Since you implement the constructor in your derived class, why don't you call the base class constructor ?

What exact situation do you have ?

[Taz742]

@SGaist said in QObject::connect: signal not found in promoted widget with Lambda syntax:

Since you implement the constructor in your derived class, why don't you call the base class constructor ?

I dont understood...

@SGaist said in QObject::connect: signal not found in promoted widget with Lambda syntax:

What exact situation do you have ?

QObject::connect: signal not found in ImageWorker
QObject::connect: signal not found in ImageWorker

I am debuging it and its happen here:

        connect(this, &ImageWorker::finished, thread, &QThread::quit);
        connect(this, &ImageWorker::finished, this, &ImageWorker::deleteLater);

[SGaist]

explicit ImageWorker(QObject *parent = 0)
        : QObject(parent)
    {
        QThread *thread = new QThread;
       etc.

I removed #include "globalhelper.h" and it build successfully on macOS.

[Taz742]

@SGaist
There is great uncertainty... I changed

@Taz742 said in QObject::connect: signal not found in promoted widget with Lambda syntax:

    connect(this, &ImageWorker::finished, thread, &QThread::quit);
    connect(this, &ImageWorker::finished, this, &ImageWorker::deleteLater);

to

        connect(this, SIGNAL(workerFinished()), thread, SLOT(quit()));
        connect(this, SIGNAL(workerFinished()), this, SLOT(deleteLater()));

its work...