Slot executions problems in a new thread

luca

Hi all,
I got a strange problem. You can see the following code.

I have an object as this:
@
GestoreComunicazioneBase::GestoreComunicazioneBase() :
QObject(0)
{
...
...
m_thread = new QThread;
this->moveToThread(m_thread);
m_thread->start();
...
...
}
@

and another object that Inherit GestoreComunicazioneBase :

@
GestoreComunicazioneEmh::GestoreComunicazioneEmh() :
{
QTimer::singleShot(10000, this, SLOT(leggiElencoObis()));
}
@

where leggiElencoObis() is a slot of GestoreComunicazioneEmh.

When executing I get the following error message:
@
Object::connect: No such slot GestoreComunicazioneBase::leggiElencoObis() in ...
@

so it seems it's looking for GestoreComunicazioneBase::leggiElencoObis() while the slot is GestoreComunicazioneEmh::leggiElencoObis() .

koahnig

Do you have a "Q_OBJECT":http://developer.qt.nokia.com/doc/qt-4.8/qobject.html#Q_OBJECT macro also in GestoreComunicazioneEmh class definition?

tobias.hunger

Are you missing the Q_OBJECT macro?

luca

Now I have:
@
class GestoreComunicazioneEmh : public GestoreComunicazioneBase
{
Q_OBJECT
public:
GestoreComunicazioneEmh()
...
...
@

But with Q_OBJECT the compilation fails:
@
Desktop_Qt_4_7_4_for_GCC__Qt_SDK__Debug/../satellite/gestorecomunicazioneemh.cpp:10: undefined reference to `vtable for GestoreComunicazioneEmh'
@

I think it's should be a very stupid problem but I can't find it...

lgeyer

Re-run qmake. If your class is defined within a <code>.cpp</code> file make sure you <code>#include "filename.moc"</code>.

luca

Ok, the problem was the missing Q_OBJECT but to solve compilation problem I had to remove all build directory...

luca

It seems that "Rebuild project" in QtCreator was not enough...

Thanks all!

favoritas37

So is it solved? Because it seems that you haven't added the QObject as base class of GestoreComunicazioneEmh:

@
class GestoreComunicazioneEmh : public QObject, public GestoreComunicazioneBase
{
Q_OBJECT
public:
GestoreComunicazioneEmh(QObject* parent=NULL) : QObject(parent) {}
};
@

luca

Yes I solved by adding Q_OBJECT (a very stupid question :-) ) but when adding it the project building failed also after "Rebuilding it".
To solve the problem I also had to remove all files (Makefile too ) in build directory.

luca

QObject is in GestoreComunicazioneBase:
@
class GestoreComunicazioneBase : public QObject
{
Q_OBJECT
public:
...
...
@

goetz

[quote author="favoritas37" date="1327329544"]So is it solved? Because it seems that you haven't added the QObject as base class of GestoreComunicazioneEmh:

@
class GestoreComunicazioneEmh : public QObject, public GestoreComunicazioneBase
{
Q_OBJECT
public:
GestoreComunicazioneEmh(QObject* parent=NULL) : QObject(parent) {}
};
@[/quote]

This is WRONG! GestoreComunicazioneBase already inherits from QObject, so GestoreComunicazioneEmh is also a QObject subclass, albeit not a direct child class. Adding QObject to the inheritance list makes GestoreComunicazioneEmh in fact inherit from QObject twice, which is a bad, bad, bad idea.

favoritas37

Sorry Volker, i mentioned it because i haven't noticed that the base class already inherits from QObject. I wouldn't suggest to inherit twice from QObject.

goetz

[quote author="favoritas37" date="1327332502"]Sorry Volker, i mentioned it because i haven't noticed that the base class already inherits from QObject. I wouldn't suggest to inherit twice from QObject. [/quote]

No problem, everyone overlooks something now and then :) I just wanted to make sure that another potential trouble maker does sneak in :)