QObject::connect returns false

[SPlatten]

@JonB , please see the edited post which includes the derived class, sorry.

[J.Hilk]

@SPlatten your derived class will need the Q_OBJECT macro as well, if it defines slots/signals

[KroMignon]

@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 not void updateTime(long)

[JonB]

@SPlatten
class clsTimeSync : public clsSchdSrv {
Although updateTime() is only a slot and not a signal, you do not have Q_OBJECT in this class. Does it help if you do (and then rebuild from scratch)?

[JonB]

@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]

@J-Hilk , why? The class it inherits already has that.

[SPlatten]

@KroMignon , because I changed it from long to int after earlier posts.

[JonB]

@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_OBJECT in.

Can you please do that and then we will discuss why if it makes any difference?

[SPlatten]

@JonB , adding Q_OBJECT to the inherit class results in the compiler error:

undefined erference to `vtable for clsTimeSync`

[jsulm]

@SPlatten said in QObject::connect returns false:

results in the compiler error

You need to do a complete rebuild

[KroMignon]

@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.

[SPlatten]

@KroMignon , @JonB , @J-Hilk , @jsulm , ok, works now I think the missing Q_OBJECT was the issue as having cleaned out the build folder, remake, rebuild, now it works.

[JonB]

@jsulm said in QObject::connect returns false:

You need to do a complete rebuild

As we have said over & over again, it would be nice if people followed that instead of ignoring it.....

[JonB]

@SPlatten said in QObject::connect returns false:

@J-Hilk , why? The class it inherits already has that.

Q_OBJECT is a macro. You can look at what it does.

I know the rule is:

• Every class which defines signals MUST have Q_OBJECT in 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-style connect() syntax, not available in Qt4. It may be that to use SLOT() you do also need Q_OBJECT in old style? When in doubt --- and certainly if I were having a problem --- I would put Q_OBJECT into classes with slots just in case.....