#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QThread>

class Worker : public QObject {
    Q_OBJECT
    int i = 0;
public:
    Worker() : QObject() { }
signals:
    void finished(int i);
public slots:
    void process();
};

class Controller : public QObject {
    Q_OBJECT
    Worker *w;
    QThread *thr;
public:
    Controller(QObject *parent = nullptr) : QObject(parent) { }
private slots:
    void middleFinish(int i);
public slots:
    void start();
signals:
    void finished(int i);
};

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
private:
    Ui::MainWindow *ui;
    Controller _c;
};

#endif // MAINWINDOW_H

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

#include <QDebug>

void Worker::process() { finished(++i); }

void Controller::start() {
    thr = new QThread;
    w = new Worker;
    w->moveToThread(thr);
    connect(thr, &QThread::started, w, &Worker::process);
    connect(w, &Worker::finished, this, &Controller::middleFinish);
    thr->start();
}
void Controller::middleFinish(int i) {
    qDebug() << "middleFinish" << i;
    disconnect(w, &Worker::finished, this, &Controller::middleFinish);
    connect(w, &Worker::finished, this, &Controller::finished);
    connect(w, &Worker::finished, thr, &QThread::quit);
    connect(w, &Worker::finished, w, &Worker::deleteLater);
    connect(thr, &QThread::finished, thr, &QThread::deleteLater);
    thr->start();
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindow) {
    ui->setupUi(this);
    connect(&_c, &Controller::finished, this, [] (int i) { qDebug() << "finish" << i; });
    _c.start();
}

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