QObject::connect returns false
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@SPlatten said in QObject::connect returns false:
moc_clsSchdSrv.cpp does not have anything that looks like the slot, no mention of updateTime at all, why ?
Some time Qt-Creator do not detect changes is
HEADERSfiles, so moc will not be re-run.
This is why I suggest you to try to re-run yourself qmake and, if this not help, remove the build directory (as also suggested by @JonB ) to force full rebuild (with moc).But first, make sure all headers are present in
HEADERSof your PRO file.@KroMignon, I deleted the content of the build folder , checking for any hidden files, then ran clean, remake and build, same results.
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@J-Hilk , clsSchdSrv.h, still a early work in progress:
class clsSchdSrv : public QTimer { Q_OBJECT public: explicit clsSchdSrv(QObject* pParent = 0); void kick(); public slots: virtual void expired() = 0; }Sorry, should have added:
class clsTimeSync : public clsSchdSrv { public: explicit clsTimeSync(); public slots: virtual void expired(); void updateTime(int intTimeNow); } -
@J-Hilk , clsSchdSrv.h, still a early work in progress:
class clsSchdSrv : public QTimer { Q_OBJECT public: explicit clsSchdSrv(QObject* pParent = 0); void kick(); public slots: virtual void expired() = 0; }Sorry, should have added:
class clsTimeSync : public clsSchdSrv { public: explicit clsTimeSync(); public slots: virtual void expired(); void updateTime(int intTimeNow); } -
@J-Hilk , clsSchdSrv.h, still a early work in progress:
class clsSchdSrv : public QTimer { Q_OBJECT public: explicit clsSchdSrv(QObject* pParent = 0); void kick(); public slots: virtual void expired() = 0; }Sorry, should have added:
class clsTimeSync : public clsSchdSrv { public: explicit clsTimeSync(); public slots: virtual void expired(); void updateTime(int intTimeNow); }@SPlatten said in QObject::connect returns false:
clsSchdSrv.h, still a early work in progress:
I am not sure, you can declare a
slotas virtual.
I would change this to:class clsSchdSrv : public QTimer { Q_OBJECT public: explicit clsSchdSrv(QObject* pParent = 0); void kick(); public: virtual void onExpired() = 0; public slots: void expired() { onExpired(); } } -
@SPlatten said in QObject::connect returns false:
public slots:
virtual void expired() = 0;But you use
SLOT(updateTime())?Why are you showing us
clsSchdSrv? Earlier you showedclsTimeSync? -
@SPlatten your derived class will need the Q_OBJECT macro as well, if it defines slots/signals
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@SPlatten said in QObject::connect returns false:
please see the edited post which includes the derived class, sorry.
In this header signal signature is
void updateTime(int)and notvoid updateTime(long)It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)
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@SPlatten said in QObject::connect returns false:
please see the edited post which includes the derived class, sorry.
In this header signal signature is
void updateTime(int)and notvoid updateTime(long)@KroMignon said in QObject::connect returns false:
In this header signal signature is void updateTime(int) and not void updateTime(long)
That's coz he has changed per earlier on.
I agree we do not know for sure what his code is, but I think he dealt with that alteration. -
@SPlatten your derived class will need the Q_OBJECT macro as well, if it defines slots/signals
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@SPlatten said in QObject::connect returns false:
please see the edited post which includes the derived class, sorry.
In this header signal signature is
void updateTime(int)and notvoid updateTime(long)@KroMignon , because I changed it from long to int after earlier posts.
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@SPlatten said in QObject::connect returns false:
@J-Hilk , why? The class it inherits already has that.
That's not how it works. Which is why I said to try putting
Q_OBJECTin.Can you please do that and then we will discuss why if it makes any difference?
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@SPlatten said in QObject::connect returns false:
@J-Hilk , why? The class it inherits already has that.
That's not how it works. Which is why I said to try putting
Q_OBJECTin.Can you please do that and then we will discuss why if it makes any difference?
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@JonB , adding Q_OBJECT to the inherit class results in the compiler error:
undefined erference to `vtable for clsTimeSync`@SPlatten said in QObject::connect returns false:
results in the compiler error
You need to do a complete rebuild
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@SPlatten said in QObject::connect returns false:
why? The class it inherits already has that.
Because it is a Qt recommendation (cf. https://doc.qt.io/qt-5/metaobjects.html)
The meta-object system is based on three things:
- The QObject class provides a base class for objects that can take advantage of the meta-object system.
- The Q_OBJECT macro inside the private section of the class declaration is used to enable meta-object features, such as dynamic properties, signals, and slots.
- The Meta-Object Compiler (moc) supplies each QObject subclass with the necessary code to implement meta-object features.
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@JonB , adding Q_OBJECT to the inherit class results in the compiler error:
undefined erference to `vtable for clsTimeSync` -
@SPlatten said in QObject::connect returns false:
results in the compiler error
You need to do a complete rebuild
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@SPlatten said in QObject::connect returns false:
@J-Hilk , why? The class it inherits already has that.
Q_OBJECTis a macro. You can look at what it does.I know the rule is:
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Every class which defines signals MUST have
Q_OBJECTin that class definition. Inheritance from parent is not what it's about. -
Normally I believe slot-only classes do not have to have
Q_OBJECT. HOWEVER I only work with the new-styleconnect()syntax, not available in Qt4. It may be that to useSLOT()you do also needQ_OBJECTin old style? When in doubt --- and certainly if I were having a problem --- I would putQ_OBJECTinto classes with slots just in case.....
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