Can I search for files via QtConcurrent?
I need to find files on my HDD (recursively).
But it takes a long of time and GUI freezes.
I try to solve it via QtConcurrent:
connect(&watcher, SIGNAL(finished()), this, SLOT(loadFinished()));
future = QtConcurrent::run(&MainWindow::searchForFiles, lineEditInDir->text()); // in .h QFuture<QFileInfoList> future;
QFileInfoList MainWindow::searchForFiles(const QString &startDir)
foreach (QString file, dir.entryList(QStringList("*.svg"), QDir::Files))
list += QFileInfo(startDir+"/"+file);
foreach (QString subdir, dir.entryList(QDir::AllDirs | QDir::NoDotAndDotDot))
list += searchForFiles(startDir+"/"+subdir);
fileList = future.result();
All works fine, I think, but I can't cancel it. future.cancel() didn't work, because I use QtConcurrent::run().
And i don't know how to put files search into QtConcurrent::mapped(), which can be canceled.
I think it would be useless to use QtConcurrent for this. QtConcurrent is suitable for problems that are are easy to parallelize. Searching your HDD will have I/O as the bottleneck, so using multiple threads to do that is not efficient. The threads will end up waiting for each other.
So, I would use either a QObject derived worker that you move to a vanilla [[doc:QThread]], or a [[doc:QRunnable]] subclass in conjunction with [[doc:QThreadPool]]. Because you seem to need cancel capabilities, I think the QThread route would be easiest.
Using QtConcurrent can even worse the situation as OS caches might get flushed once the next thread is running and the data needs to be re-read if the first thread is active again.