main.cpp Example File

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  #include <QtWidgets>
  #include <QtConcurrent>

  #include <functional>

  using namespace QtConcurrent;

  int main(int argc, char **argv)
  {
      QApplication app(argc, argv);

      const int iterations = 20;

      // Prepare the vector.
      QVector<int> vector;
      for (int i = 0; i < iterations; ++i)
          vector.append(i);

      // Create a progress dialog.
      QProgressDialog dialog;
      dialog.setLabelText(QString("Progressing using %1 thread(s)...").arg(QThread::idealThreadCount()));

      // Create a QFutureWatcher and connect signals and slots.
      QFutureWatcher<void> futureWatcher;
      QObject::connect(&futureWatcher, &QFutureWatcher<void>::finished, &dialog, &QProgressDialog::reset);
      QObject::connect(&dialog, &QProgressDialog::canceled, &futureWatcher, &QFutureWatcher<void>::cancel);
      QObject::connect(&futureWatcher,  &QFutureWatcher<void>::progressRangeChanged, &dialog, &QProgressDialog::setRange);
      QObject::connect(&futureWatcher, &QFutureWatcher<void>::progressValueChanged,  &dialog, &QProgressDialog::setValue);

      // Our function to compute
      std::function<void(int&)> spin = [](int &iteration) {
          const int work = 1000 * 1000 * 40;
          volatile int v = 0;
          for (int j = 0; j < work; ++j)
              ++v;

          qDebug() << "iteration" << iteration << "in thread" << QThread::currentThreadId();
      };

      // Start the computation.
      futureWatcher.setFuture(QtConcurrent::map(vector, spin));

      // Display the dialog and start the event loop.
      dialog.exec();

      futureWatcher.waitForFinished();

      // Query the future to check if was canceled.
      qDebug() << "Canceled?" << futureWatcher.future().isCanceled();
  }