Agfdhyk

Hi I have a class named search and this class has two member functions. The consumer and the producer. This is the way I have activated these functions as two threads in qt.

thread1 = new QThread();

thread2 = new QThread();

mySearch = new Search() ;



mySearch->moveToThread(thread1);



mySearch->moveToThread(thread2);





connect(mySearch, SIGNAL(workRequested()), thread1, SLOT(start()));

connect(mySearch, SIGNAL(workRequested()), thread2, SLOT(start()));



connect(thread1, SIGNAL(started()),mySearch, SLOT(producer()));

connect(thread2, SIGNAL(started()),mySearch, SLOT(consumer()));



connect(mySearch, SIGNAL(finishedscan()), thread1, SLOT(quit()), Qt::DirectConnection);

connect(mySearch, SIGNAL(finishedscan()), thread2, SLOT(quit()), Qt::DirectConnection);

But, it seems that only one is activated. How should I activate both. Please let me know with an example.

Thanks.

This is a simple example to run the two methods of the same object in two different threads. Assuming your Search class looks like this:

class Search : public QObject

{

    Q_OBJECT



public:

    void producer();

    void consumer();



signals:

    void workRequested();

    void finishedscan();

};

You would create a second class like this:

class Worker : public QObject

{

    Q_OBJECT



public:

    Worker(std::function<void()> task) :

        QObject{},

        _task{std::move(task)}

    {}



public slots:

    void work() {

        _task();

    }



private:

    std::function<void()> _task;

};

And now you can implement the start:

thread1 = new QThread();

thread2 = new QThread();

mySearch = new Search();

auto worker1 = new Worker(std::bind(&Search::producer, mySearch));

auto worker2 = new Worker(std::bind(&Search::consumer, mySearch));



worker1->moveToThread(thread1);

worker2->moveToThread(thread2);



connect(mySearch, SIGNAL(workRequested()), thread1, SLOT(start()));

connect(mySearch, SIGNAL(workRequested()), thread2, SLOT(start()));



connect(thread1, SIGNAL(started()),worker1, SLOT(work()));

connect(thread2, SIGNAL(started()),worker2, SLOT(work()));



connect(mySearch, SIGNAL(finishedscan()), thread1, SLOT(quit()), Qt::DirectConnection);

connect(mySearch, SIGNAL(finishedscan()), thread2, SLOT(quit()), Qt::DirectConnection);

Important: While this solution solves how to start the two tasks on different threads, stopping won't work yet as QThread::quit only works if the thread returns to the eventloop! If your producer/consumer methods do not return to the eventloop and use it to perform tasks, write so in the comments and I will update the answer to handle that case as well.

EDIT: Since stopping i the above solution only works, if producer/consumer return to the eventloop - which is not the case according to OP, you have to manually notify the worker that it should stop working to gracefully quit the thread.

For the first solution, your worker has to periodically check, if it should stop working. For example:

MySearch::producer() {

    while(!QThread::currentThread()->isInterruptionRequested() {

        //do some work 

    }

}

And secondly, you have to adjust how you quit the thread:

connect(mySearch, &MySearch::finishedscan, thread1, [thread1](){

    thread1->requestInterruption();

    thread1->quit();

}, Qt::DirectConnection);

Note: Regardless of how you quit your threads, you should always wait for them in the main thread to finish their work before exiting:

thread1->wait();

Finally, you mentioned in the comments that you use CTRL+C to quit the application - make shure to register a signal handler to catch SIGINT and stop you application gracefully, as the default SIGINT will just terminate it, without proper cleanup