Do you think PROTECTED QThread::sleep() method should be made PUBLIC ?



  • To create a new thread, it is more and more advocated not to subclass QThread but instead to create a Worker class and then to move the worker object to the new thread by using moveToThread().
    I prefer this method too. It makes the code much more clear and logic. However there is a drawback. We can’t use static QThread::sleep() method anymore because this method is protected.
    There are always workarounds like the one I propose below but I’d like to know if you think as I do that Qt should now consider making this static method PUBLIC so that we can simply sleep like that in the worker code ? :
    @
    QThread::currentThread()->sleep(5);
    @

    The workaround below consists in subclassing QThread to MThread to make sleep() public and then to sleep by casting currentThread() to MThread before calling MThread public sleep().

    @
    class MThread : public QThread {
    Q_OBJECT
    public:
    MThread(QObject *parent) : QThread(parent) {}
    static void sleep(unsigned long secs) { QThread::sleep(secs);}
    };

    class Worker : public QObject {
    Q_OBJECT
    public :
    Worker(){}
    Q_INVOKABLE void task1() {
    qDebug() << "Worker::task1() - begin - Thread=" << QThread::currentThreadId();
    static_cast<MThread *>(QThread::currentThread())->sleep(5);
    qDebug() << "Worker::task1() - end - Thread=" << QThread::currentThreadId();
    }
    ….
    }

    int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    qDebug() << "main() - ThreadId =" << QThread::currentThreadId();
    Worker *worker = new Worker;
    QThread *thread = new QThread;
    thread->start();
    worker->moveToThread(thread);
    QMetaObject::invokeMethod(worker, "task1");
    ….
    }
    @

    Also, if you can think about a more simple workaround, please let me know.

    Gilles, Paris


  • Moderators

    sleep() is made public in Qt 5: http://doc-snapshot.qt-project.org/5.0/qthread.html -- That doesn't help users of Qt 4.8, unfortunately.

    If your code involves a repeating loop, with sleeping between each iteration, you can try using QTimer to call the function at regular intervals



  • Thanks for the info. That's good news.


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