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Question

I'm not able to receive my custom signal in the supposed SLOT . Here is my code:

mainwindow.h :

class HistoryItem {
    public:
        QString channel;
};


class dbThread : public QObject
{
     Q_OBJECT

public:
     dbThread();

signals:

void historyLoaded(QList<HistoryItem*> innerResult);


class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

public slots:
    void historyLoaded(const QList<HistoryItem*> innerResult);

mainwindow.cpp :

connect(dbtrad, SIGNAL(historyLoaded(QList<HistoryItem*>*)), this, SLOT(historyLoaded(QList<HistoryItem*>*)));

void MainWindow::historyLoaded(QList<HistoryItem*> innerResult) {
    qDebug() << "historyLoaded()...";
}

And this is how I emit the signal:

QList<HistoryItem*> innerResult;
while (queryInner.next()) {
    QString channelIDInner = queryInner.value(0).toString();

    HistoryItem* item = new HistoryItem();
    item->channel = channelIDInner;

    innerResult.append(item);
}
qDebug() << "DONE LOADING.....";
emit historyLoaded(innerResult);

However, qDebug() << "historyLoaded()..."; is never executed.

Any ideas what the problem could be?

Answer 1

It seems you're using threads. Using QList when signaling across threads (or using Qt::QueuedConnection in general) requires some extra work. Basically you need to define the QList<T> type using typedef and then register it using qRegisterMetaType :

typedef QList<HistoryItem*> HistoryList_t;
...
qRegisterMetaType<HistoryList_t>("HistoryList_t");

Then use this type in your signals and slots:

public slots:
    void historyLoaded(const HistoryList_t &list);

Answer 2

Check return value of your connect , it should fail. There is an extra * in SIGNAL(historyLoaded(QList<HistoryItem*>*)) , should be SIGNAL(historyLoaded(QList<HistoryItem*>)) . Fix your SLOT() too.