Call QtConcurrent::run as slot

Question

I'am trying to call asynchrone function like slot but when i click on the button nothing happen.

Code:

connect(ui->Button1, SIGNAL(clicked()), this, SLOT(QtConcurrent::run(func1)));

func is declared in private slot.

When i call function normally, everything work nice but the app is frozen during some time until the function completes.

connect(ui->Button1, SIGNAL(clicked()), this, SLOT(func1()));

Answer 1

connect has implicit Qt::ConnectionType parameter. It will be defined as Qt::QueuedConnection when sender and receiver are in different threads. You can use QObject::moveToThread to move worker to another thread.
If for some reason you want use QtConcurrent::run here - you can use it inside func1 implementation.
Check both versions:

class Worker : public QObject {
 public:
  void DoSlowCalculation() {
    qDebug() << "Worker::DoSlowCalculation thread:" << QThread::currentThreadId();
    QThread::msleep(2000);  // 2 sec
    qDebug() << "Worker::DoSlowCalculation finished";
  }
};

class ConcurrentExecutor : public QObject {
 public:
  void DoSlowCalculation() {
    qDebug() << "ConcurrentExecutor::DoSlowCalculation thread:" << QThread::currentThreadId();
    QThread::msleep(2000);  // 2 sec
    qDebug() << "ConcurrentExecutor::DoSlowCalculation finished";
  }
  void DoSlowCalculationConcurrent() {
    QtConcurrent::run(this, &ConcurrentExecutor::DoSlowCalculation);
  }
};

int main(int argc, char** argv) {
  QApplication app(argc, argv);
  
  qDebug() << "Main thread:" << QThread::currentThreadId();
  
  QThread worker_thread;
  Worker worker;
  worker.moveToThread(&worker_thread);
  worker_thread.start();

  QPushButton btn;
  btn.setText("Click to perform slow calculation");

  QObject::connect(&btn, &QAbstractButton::clicked, &worker,
                   &Worker::DoSlowCalculation);

  ConcurrentExecutor concurr_executor;
  QObject::connect(&btn, &QAbstractButton::clicked, &concurr_executor,
                   &ConcurrentExecutor::DoSlowCalculationConcurrent);

  worker_thread.start();

  QObject::connect(&app, &QCoreApplication::aboutToQuit, &worker_thread,
                   &QThread::quit);
  btn.show();
  return app.exec();
}

P.S. Strongly suggest to stop using SIGNAL and SLOT macros, that's Qt4 way to connect. More info on this topic here.