Qtconcurrent - Easy way to start a second thread from gui thread - c++

Question

I would like to find an easy way to start a lengthy operation from my application's main gui thread. I have his exporter object that is not affiliated to any thread.
void closeExporter()
{
// Run closing of object in a different thread:
QFuture<void> future = QtConcurrent::run([=]()
{
m_pExporter->close();
});
while (!future.isFinished())
{
QApplication::processEvents();
// QThread::msleep(0);
qDebug() << "waiting!";
}
}
I am not using waitForFinished() function then it blocks any my gui thread becomes unresponsive. It works fine for a while put the debug printing stop and my application will still become unresponsive. Dies somebody have an idea why this is happening?

Answer 1

I think, that you should use QFutureWatcher as a possible implementation. The following small example illustrates the usage.
#include <QApplication>
#include <QFrame>
#include <QDebug>
#include <QHBoxLayout>
#include <QPushButton>
#include <QThread>
#include <QObject>
#include <QFutureWatcher>
#include <QMessageBox>
#include <QtConcurrent>
int main(int argc, char* argv[])
{
QApplication a(argc, argv);
auto frame = new QFrame;
frame->setLayout(new QHBoxLayout);
auto btn = new QPushButton("Start Thread");
frame->layout()->addWidget(btn);
QThread::currentThread()->setObjectName("Main Thread");
QFutureWatcher<void> watcher;
QObject::connect(&watcher, &QFutureWatcher<void>::finished, [frame,btn]() {
QMessageBox::information(frame, "Done", QThread::currentThread()->objectName(), QMessageBox::StandardButton::Ok);
btn->setEnabled(true);
});
QObject::connect(btn, &QPushButton::clicked, [btn,&watcher](){
QFuture<void> future = QtConcurrent::run([]() {
QThread::msleep(6000);
qDebug() << QThread::currentThread()->objectName();
});
watcher.setFuture(future);
btn->setDisabled(true);
});
frame->show();
return a.exec();
}

Answer 2

The original code was working fine after all. Sorry to burn your time.