Signal emitted from QThread never received - c++

Question

Here are the code snippets. The thread class that will do some work:
class MyThread : public QThread
{
Q_OBJECT
public:
MyThread(QWidget* parent) : QThread(parent) {}
signals:
void results(size_t added);
private:
void run() override { emit results(7); }
};
The main window class:
class MyMain : public QMainWindow
{
Q_OBJECT
public:
MyMain(QWidget* parent = Q_NULLPTR) : QMainWindow(parent) {}
private slots:
void imagesAdded(size_t added) { qDebug() << "images added"; }
private:
void test() {
MyThread* thread = new MyThread(this);
connect(thread, &MyThread::results, this, &MyMain::imagesAdded);
connect(thread, &MyThread::finished, thread, &QObject::deleteLater);
thread->start();
}
};
In the debugger, I can see the "results" signal connects successfully and that the signal is emitted, however, it is never received.

Answer 1

you forgot to write something like moveToThread and exec() and ...
as I underestand from your question I write this example and run it:
In mythread.h
#ifndef MYTHREAD_H
#define MYTHREAD_H
#include <QObject>
#include <QThread>
class MyThread: public QThread
{
Q_OBJECT
public:
MyThread();
protected:
void run();
signals:
void results(int);
};
#endif // MYTHREAD_H
In mythread.cpp
#include "mythread.h"
MyThread::MyThread():
QThread(nullptr)
{
moveToThread(this);
}
void MyThread::run()
{
emit results(7);
exec();
}
In mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QDebug>
QT_BEGIN_NAMESPACE
namespace Ui
{
class MainWindow;
}
QT_END_NAMESPACE
class MainWindow: public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void imagesAdded(int added)
{
qDebug() << "images added" << added;
}
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
In mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "mythread.h"
MainWindow::MainWindow(QWidget *parent):
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
MyThread *thread = new MyThread();
connect(thread, &MyThread::results, this, &MainWindow::imagesAdded);
connect(thread, &MyThread::finished, thread, &QObject::deleteLater);
thread->start();
}
MainWindow::~MainWindow()
{
delete ui;
}
The output :