Hello! I am new to QT, I almost never worked with streams before, I would like to make inquiries about how to use streams correctly, in parallel, I read quite a lot, I’m not sure what I’m going to digest ...

Here is an example: there is a class identificator, .h:

class identificator:public QObject { Q_OBJECT public: identificator(); virtual ~identificator(); private: int id; private slots: void printID(); public: void setID(int i); int getID(); signals: void finished(); };

.cpp:

 #include "identificator.h" #include <stdio.h> identificator::identificator() { id=0; } identificator::~identificator() { // TODO Auto-generated destructor stub } void identificator::setID(int i) { id=i; } int identificator::getID() { return id; } void identificator::printID() { for(;;) { printf("%d\n",this->getID()); } emit finished(); }

but main.cpp:

 #include <QtCore> #include <QCoreApplication> #include <QApplication> #include "myThread.h" #include "identificator.h" #include <stdio.h> int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); printf("Hello\n"); identificator *first=new identificator(); identificator *second=new identificator(); QThread *thread1=new QThread; QThread *thread2=new QThread; first->setID(3); second->setID(4); QObject::connect(thread1, SIGNAL(started()), first, SLOT(printID())); QObject::connect(thread2, SIGNAL(started()), second, SLOT(printID())); QObject::connect(first, SIGNAL(finished()), thread1, SLOT(quit())); QObject::connect(second, SIGNAL(finished()), thread2, SLOT(quit())); thread1->start(); thread2->start(); return a.exec(); }

I expect that the numbers 3 and 4 will be displayed in the console, separately and indefinitely, but only 3 are displayed in the console when I start. Please, tell me how to get them to work in parallel? Thank you in advance!

I read that the algorithm should be something like this:

1) Create a stream. 2) Creating an object and transfer to the stream. 3) Installation of signal-slot communications. 4) Run a stream with a given priority.

Therefore added as advised: moveToThread ()

 int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); printf("Hello\n"); identificator *first=new identificator(); identificator *second=new identificator(); QThread *thread1=new QThread; QThread *thread2=new QThread; first->setID(3); second->setID(4); first->moveToThread(thread1); second->moveToThread(thread2); QObject::connect(thread1, SIGNAL(started()), first, SLOT(printID())); QObject::connect(thread2, SIGNAL(started()), second, SLOT(printID())); QObject::connect(first, SIGNAL(finished()), thread1, SLOT(quit())); QObject::connect(second, SIGNAL(finished()), thread2, SLOT(quit())); thread1->start(); thread2->start(); return a.exec(); }

Added moveToThread () and after initialization and after connect () both options did not help ....

I would be grateful for the help.

  • And where do you bind your identificator to QThread? - Vladimir Martyanov
  • in main.cpp, via connect (), or do you need to bind to a stream inside a class? - infernalcucumber
  • And, for sure, I did not see ... - Vladimir Martyanov
  • one
    @infernalcucumber main.cpp idprinter.h - yrHeTaTeJlb
  • one
    @infernalcucumber, I alternate 3 and 4. Although I must say at home and at work, it looks different. Houses - 33434434343343, at work - 3333333444444433333 - yrHeTaTeJlb

1 answer 1

After connections try adding

 first->moveToThread(thread1); second->moveToThread(thread2);

However, I recommend looking towards QtConcurrent::run() . This is a higher level thing, maybe it will be a little easier with it at first. There is also QRunnable + QThreadPool , which for some tasks may be more convenient than QThread .

How Qthread used Qthread best seen in the help, there everything is very accessible described. If in a nutshell, you need to create a class, the slot of which will be executed in a separate thread (in the documentation it was called Worker ). Then an object of this class is placed in the stream ( worker->moveToThread(&workerThread); ). And when any signal activates the slot of our worker , this slot will run in a separate thread.

  • Added moveToThread (), did not help ... I tried the variant with QtConcurrent :: run () - also, all threads are blocked after starting the first ... - infernalcucumber
  • @infernalcucumber, and if you create a QThreadPool and call maxThreadCount, what happens? - yrHeTaTeJlb
  • QThreadPool for some reason works similarly - the function of the first thread is executed first, then the second, consistently - infernalcucumber
  • @infernalcucumber, maxThreadCount what returns? - yrHeTaTeJlb
  • link - tried from there to call maxThreadCount() before start . The console displays: "1". - infernalcucumber