multithreading - Qt C++ - How to pass data from a worker thread to main thread? -

i trying perform interthread communication in qt (c++). have worker thread calculations , want workerthread return results main thread when done. therefor use connect, know debugging, signal being emit slot isn t being executed , don t understand why.

the relevant pieces of code:

webcamclass::webcamclass(qobject *parent) : qobject(parent) {       workerthread = new qthread(this);     workerclassobj = new workerclass();      //connect image     connect(workerclassobj, signal(mysignal(qpixmap)), this, slot(myslot(qpixmap)));      //connect(&workerclassobj, workerclass::mysignal(qpixmap), this, webcamclass::myslot(qpixmap));       connect( workerthread, signal(started()), workerclassobj, slot(getimage()) );     workerclassobj->movetothread(workerthread);   }  void webcamclass:: foo() {        workerthread->start(); }  void workerclass::getimage() {     qint64 successfailwrite;     qimage img;     qpixmap pixmap;      ... stuff pixmap...      qdebug()<<"going emit result";      emit mysignal(pixmap);      qdebug()<<"emitted"; }   void webcamclass::myslot(qpixmap p) {qdebug()<<"this message should displayed"; } 

the corresponding header files:

   class workerclass : public qobject     {         q_object     private:      public:         explicit workerclass(qobject *parent = nullptr);       signals:         void mysignal(qpixmap);     };    webcamclass::webcamclass(qobject *parent) : qobject(parent) {     q_object public:     explicit webcamclass(qobject *parent = nullptr);  public slots:     void myslot(qpixmap p);  private:      qthread *workerthread;     workerclass *workerclassobj;   }; 

the code above outputs:

going emit result emitted 

but unfortunately doesn t output this message should displayed.

webcamclass belongs parent thread, while workerclass belngs -you guessed it- worker thread.

could explain how setup connect myslot() gets triggered?

thanks!

in code pasted in pastebin.com/uppfrnet have getvideoframe method uses while (1). if method called, runs time , blocks event loop handling signals. can solve in many ways, think best practice replace while(1) else.

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