c++ - Cannot connect slots from another class -

i try write little application experiments , more. write in own file (menu -> menu.cpp etc.). want create menu action, works interacting action doesnt. thats i've done far:

menu.cpp

#include "menu.h" #include <qmenubar> #include <qmenu> #include <qaction>   void menu::setupmenu(qmainwindow *window) {     qmenubar *mb = new qmenubar();     qmenu *filemenu = new qmenu("file");     qaction *newact = new qaction("new...", window);     window->connect(newact, signal(triggered()), this, slot(newfile()));     filemenu->addaction(newact);     mb->addmenu(filemenu);     window->setmenubar(mb); }  void menu::newfile() {     printf("hello world!"); } 

menu.h

#ifndef menu_h #define menu_h  #include <qobject> #include <qmainwindow> #include <qwidget> #include <qmenubar>  class menu : public qobject { public:     void setupmenu(qmainwindow *window); private slots:     void newfile(); };  #endif // menu_h 

but not printing out 'hello world', message is:

qobject::connect: no such slot qobject::newfile() in ../from scratch written ui app c++/src/ui/menu.cpp:11

what can fix this?

~ jan

class menu : public qobject

menu qobject needs use q_object macro.

see qt5 - qobject documentation:

the q_object macro must appear in private section of class definition declares own signals , slots or uses other services provided qt's meta-object system.

next, there confusion in connect call. here signature of static connect function.

qt5 - static qobject::connect:

qobject::connect(const qobject * sender, const char * signal, const qobject * receiver, const char * method, qt::connectiontype type = qt::autoconnection)

you can see takes 5 parameters (object pointer, signal, object pointer, signal/slot) , 5th parameter defaulted.

there member function connect.

qt5 - qobject::connect:

qobject::connect(const qobject * sender, const char * signal, const char * method, qt::connectiontype type = qt::autoconnection) const

this takes 4 parameters (object pointer, signal, signal/slot) , 4th parameter defaulted.

your code:

window->connect(newact, signal(triggered()), this, slot(newfile()));

you're calling the connect member function of window you're passing parameters static connect function.

what can fix this?

figure out you're trying , make appropriate call.

for example: connect qaction signal slot in menu either call static function follows.

connect(newact, signal(triggered()), this, slot(newfile())); 

or using member function.

connect(newact, signal(triggered()), slot(newfile()));