Hi, I got the error in the title running a class derived from QNetworkAccessManager to download and save files. It works fine except when requesting a large number of file (600~). Here the implementation (quite common):

Qt Code: 
  1. FileDownloader::FileDownloader(QObject *parent) :
  2.     QNetworkAccessManager(parent)
  3. {
  4. }
  5.  
  6. FileDownloader::~FileDownloader()
  7. {
  8.     deleteLater();
  9. }
  10.  
  11. void FileDownloader::setPath(const QString &path)
  12. {
  13.     mPath = path;
  14. }
  15.  
  16. void FileDownloader::setFileName(const QString &fileName)
  17. {
  18.     mFileName = fileName;
  19. }
  20.  
  21. void FileDownloader::setUrl(const QString &url)
  22. {
  23.     mUrl = url;
  24. }
  25.  
  26. void FileDownloader::download()
  27. {
  28.     file = new QFile;
  29.     file->setFileName(mPath + QDir::separator() + mFileName);
  30.  
  31.     if(file->exists())
  32.         if(!file->remove()) {
  33.             qDebug() << file->errorString();
  34.             return;
  35.         }
  36.  
  37.     file->open(QIODevice::WriteOnly);
  38.  
  39.     QNetworkRequest request;
  40.     request.setUrl(QUrl(mUrl));
  41.     reply = get(request);
  42.  
  43.     connect(reply, SIGNAL(downloadProgress(qint64,qint64)), this, SLOT(onDownloadProgress(qint64,qint64)));
  44.     connect(this, SIGNAL(finished(QNetworkReply*)), this, SLOT(onFinished(QNetworkReply*)));
  45.     connect(reply, SIGNAL(readyRead()), this, SLOT(onReadyRead()));
  46.     connect(reply, SIGNAL(finished()), this, SLOT(onReplyFinished()));
  47. }
  48.  
  49.  
  50. void FileDownloader::onFinished(QNetworkReply *reply)
  51. {
  52.     switch(reply->error()) {
  53.     case QNetworkReply::NoError:
  54.         qDebug() << "Downloaded:" << file->fileName();
  55.         break;
  56.  
  57.     default:
  58.         qDebug(reply->errorString().toLatin1());
  59.     }
  60.  
  61.     if(file->isOpen()) {
  62.         file->close();
  63.         file->deleteLater();
  64.     }
  65. }
  66.  
  67. void FileDownloader::onReadyRead()
  68. {
  69.     file->write(reply->readAll());
  70. }
  71.  
  72. void FileDownloader::onReplyFinished()
  73. {
  74.     if(file->isOpen()) {
  75.         file->close();
  76.         file->deleteLater();
  77.     }
  78. }
  79.  
  80. void FileDownloader::onDownloadProgress(qint64, qint64)
  81. {
  82.     qDebug(QString::number(bytesRead).toLatin1() + " - " + QString::number(bytesTotal).toLatin1());
  83. }
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I'm calling it this way:

Qt Code: 
  1. foreach(QString file, files) {
  2.     FileDownloader * downloader = new FileDownloader(this);
  3.     downloader->setUrl(/*...*/);
  4.     downloader->setPath(/*...*/);
  5.     downloader->setFileName(/*...*/);
  6.     downloader->download();
  7. }
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Searching the web I read that a solution should be QRunnable, but I'm using it in the wrong way:
* had subclassed QRunnable:
Qt Code: 
  1. class FileDownloader : public QNetworkAccessManager, public QRunnable
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* renamed FileDownloader::download() in FileDownloader::run()
* modified calling routine:
Qt Code: 
  1. foreach(QString file, files) {
  2.     FileDownloader * downloader = new FileDownloader(this);
  3.     downloader->setUrl(/*...*/);
  4.     downloader->setPath(/*...*/);
  5.     downloader->setFileName(/*...*/);
  6.     QThreadPool::globalInstance()->start(downloader); // <- new version
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In console I got repetition of the following error:

QObject: Cannot create children for a parent that is in a different thread.
(Parent is FileDownloader(0x13297e0), parent's thread is QThread(0x118c420), current thread is QThread(0x13525d0)
Any help will be very appreciated. Thanks.