c++ - Qt 5.1 QML property through Threads -

for purpose of resolution, i've created testapp repeat same problem have.

i'm porting software qt 4.8 qt 5.1.

my first program multithreaded, , working smoothly qml, provided classes thread safe. message :

qobject::connect: no such slot testapp::run() in ..\threadingtest\main.cpp:21 qqmlengine: illegal attempt connect testapp(0x29cfb8) in different thread qml engine qqmlengine(0x2f3e0f8). 

this code reproduce error :

main.cpp :

#include <qtgui/qguiapplication> #include <qqmlcontext> #include <qthread> #include "qtquick2applicationviewer.h" #include "testapp.h"  int main(int argc, char *argv[]) {     int out;      qguiapplication app(argc, argv);      qtquick2applicationviewer viewer;      testapp * testapp = new testapp();      qthread * testappthread;      testappthread = new qthread();      qobject::connect(testappthread, signal(started()), testapp, slot(run()));      testapp->movetothread(testappthread);      testappthread->start();      viewer.rootcontext()->setcontextproperty("testapp", testapp);      viewer.setmainqmlfile(qstringliteral("qml/threadingtest/main.qml"));     viewer.showexpanded();      out = app.exec();      testappthread->quit();     testappthread->wait();      delete testapp;     delete testappthread;      return out; } 

testapp.h :

#ifndef testapp_h #define testapp_h  #include <qobject> #include <qstring> #include <qtimer> #include <qreadwritelock>  #define helloworld "hello world !"  extern qreadwritelock helloworldlock;  class testapp : public qobject {     q_object      q_property(qstring helloworld read gethelloworld write sethelloworld notify helloworldchanged) public:     explicit testapp(qobject *parent = 0);      virtual ~testapp();      qstring gethelloworld();      void sethelloworld(qstring);  public slots:      void run();      void togglehelloworld();  signals:      void helloworldchanged();  private:      qstring m_helloworld;     qtimer * m_timer;  };  #endif // testapp_h 

testapp.cpp :

#include "testapp.h"  qreadwritelock helloworldlock(qreadwritelock::recursive);  testapp::testapp(qobject *parent) :     qobject(parent) {     helloworldlock.lockforwrite();     m_helloworld = helloworld;     helloworldlock.unlock();      m_timer = new qtimer(this);      connect(m_timer, signal(timeout()), this, slot(togglehelloworld())); }  testapp::~testapp() {     m_timer->stop();      delete m_timer; }  qstring testapp::gethelloworld() {     helloworldlock.lockforread();     qstring out = m_helloworld;     helloworldlock.unlock();      return out; }  void testapp::sethelloworld(qstring text) {     helloworldlock.lockforwrite();     m_helloworld = text;     helloworldlock.unlock();      emit helloworldchanged(); }  void testapp::run() {     m_timer->start(1000); }  void testapp::togglehelloworld() {     helloworldlock.lockforwrite();     if(m_helloworld == "") {         m_helloworld = helloworld;     }     else {         m_helloworld = "";     }     helloworldlock.unlock();      emit helloworldchanged(); } 

main.qml :

import qtquick 2.0  rectangle {     width: 360     height: 360     text {         text: testapp.helloworld         anchors.centerin: parent     }     mousearea {         anchors.fill: parent         onclicked: {             qt.quit();         }     } } 

my program quite complex (a lot of properties , classes share interface) , wouldn't have create interface class connect properties... have suggestions cope issue ?

you don't need thread app cause in qt5, qml 2 engine massively multithreaded, launch qquickview, expose c++ parts need context, set qml file in it, , show(). it's sufficient. don't try modify qml thread yourself, more complex in qml1.