将工作线程信号与 MainWindow 插槽 (Qt5) 连接时出错

Question

I want to write a simple Application which launches a thread to do some computations. The worker thread should periodically send signals to the MainWindow to inform it about the current state of progress. In order to implement the worker thread, I subclass QThread and reimplement the run method. When I compile the program using QTCreator, I always get these two errors:

In the Header file of Worker , which implements the working thread:

.../worker.h:7: error: undefined reference to `vtable for Worker'

In the Source file of MainWindow , when I try to connect the Worker signal to the MainWindow slot:

.../worker.cpp:23: error: undefined reference to `Worker::updateLabelSig(int)'

Worker.h

#ifndef WORKER_H
#define WORKER_H

#include <QThread>
#include <vector>

class Worker : public QThread
{
    Q_OBJECT

    void run() override;
private:
    void computeNumbers();
    std::vector<int> foundNumbers;
    int upperLimit;
signals:
    void updateLabelSig(int);
};

#endif // WORKER_H

Worker.cpp

#include "worker.h"

void Worker::run(){
    exec();
    computeNumbers();
}

void Worker::computeNumbers(){
    upperLimit=1e5;
    foundNumbers.push_back(1);
    for(int i=2; i<upperLimit; i++){
/////////////do some calculations and emit regular signals to inform main window///////////////////
        if(i%10000==0)
            emit updateLabelSig(i);
    }
}

In the MainWindow class, I have a button which should launch the thread if clicked:

MainWindow.cpp :

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QPushButton>
#include <QLabel>
#include "worker.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_mainbutton_clicked()
{
    Worker* w=new Worker;
    QObject::connect(w,SIGNAL(Worker::updateLabelSig(int)),this,SLOT(updateLabel(int)));
    w->start();
}

void MainWindow::updateLabel(int i){
    findChild<QLabel*>("mainlabel")->setText(QString("Numbers searched so far: ")+QString::number(i));
}

Answer 1

Ok, it turned out that I simply needed to rerun qmake in order to get things to work. When I first wrote the header file worker.h I forgot to add the Q_OBJECT macro which I added later. However, I didn't run qmake .