Worker QObjects - QThread::quit() while there are events in the event queue test

main.cpp

#include <QtWidgets>

//QThread wrapper for safe destruction
//see http://stackoverflow.com/a/19666329
class Thread : public QThread {
   using QThread::run; // final
public:
   Thread(QObject * parent = 0) : QThread(parent) {}
   ~Thread() { quit(); wait(); }
};

class Producer : public QObject{
    Q_OBJECT
public:
    explicit Producer(QObject* parent= nullptr):QObject(parent){
        timer.setInterval(250);
        QObject::connect(&timer, &QTimer::timeout, [this]{
            emit ProducedNewCount(counter++);
        });
        timer.start();
    }
    ~Producer() = default;
    Q_SIGNAL void ProducedNewCount(int counter);
private:
    int counter = 0;
    QTimer timer{this};
};

class Consumer : public QObject{
    Q_OBJECT
public:
    explicit Consumer(QObject* parent= nullptr):QObject(parent){}
    ~Consumer() = default;
    Q_SLOT void ConsumeCount(int counter){
        emit ConsumingCount(counter);
        //some heavy operation to make consumer slower than producer
        QThread::sleep(1);
    }
    Q_SIGNAL void ConsumingCount(int counter);
};

int main(int argc, char* argv[]){
    QApplication a(argc, argv);
    
    Producer* workerProducer = new Producer();
    Thread threadProducer;
    QObject::connect(&threadProducer, &Thread::finished,
                     workerProducer, &QObject::deleteLater);
    workerProducer->moveToThread(&threadProducer);
    threadProducer.start();
    
    Consumer* workerConsumer = new Consumer();
    Thread threadConsumer;
    QObject::connect(&threadConsumer, &Thread::finished,
                     workerConsumer, &QObject::deleteLater);
    workerConsumer->moveToThread(&threadConsumer);
    threadConsumer.start();
    
    QObject::connect(workerProducer, &Producer::ProducedNewCount,
                     workerConsumer, &Consumer::ConsumeCount);
    
    //set up GUI
    QWidget widget;
    QVBoxLayout vLayout(&widget);
    QTextEdit textEdit;
    QHBoxLayout hLayout;
    QPushButton buttonQuitProducer("Quit Producer Thread");
    QPushButton buttonQuitConsumer("Quit Consumer Thread");
    hLayout.addWidget(&buttonQuitProducer);
    hLayout.addWidget(&buttonQuitConsumer);
    vLayout.addWidget(&textEdit);
    vLayout.addLayout(&hLayout);
    
    QObject::connect(workerProducer, &Producer::ProducedNewCount,
                     &textEdit, [&](int counter){
        textEdit.append(QStringLiteral("<font color=\"red\">Producer:\tNew Counter %1</p>").arg(counter));
    });
    QObject::connect(workerConsumer, &Consumer::ConsumingCount,
                     &textEdit, [&](int counter){
        textEdit.append(QStringLiteral("<font color=\"blue\">Consumer:\tNew Counter %1</p>").arg(counter));
    });
    QObject::connect(&buttonQuitProducer, &QPushButton::clicked,
                     &threadProducer, &Thread::quit);
    QObject::connect(&buttonQuitConsumer, &QPushButton::clicked,
                     &threadConsumer, &Thread::quit);
    
    widget.show();
    return a.exec();
}

#include "main.moc"