Undefined reference to staticMetaObject

[Christina123]

Hello, I receive errors about Undefined reference to staticMetaObject when I have a class that is derived from a parent class which inherits QObject. I am wondering why is it?

[JKSH]

@Christina123 said in Undefined reference to staticMetaObject:

I receive errors about Undefined reference to staticMetaObject

"Undefined reference" means that you have something that is declared but not defined. See https://www.cprogramming.com/declare_vs_define.html

I am wondering why is it?

staticMetaObject is declared by the Q_OBJECT macro. It is then defined in the moc_*.cpp file that is auto-generated by moc.

So, your error means that your class has the Q_OBJECT macro but it was not processed by moc. Check 2 things:

1. By default, moc expects you to define QObject subclasses in *.h files rather than *.cpp files. If your class in in a *.cpp file, move it to a *.h file.
2. If you have done this but still get the error, you can force moc to run by running qmake.

[VRonin]

@JKSH said in Undefined reference to staticMetaObject:

you can force moc to run by running qmake

I think the question is, are you using CMake or qmake?

[JKSH]

@VRonin said in Undefined reference to staticMetaObject:

I think the question is, are you using CMake or qmake?

Ah yes, that's an important point!

[david azolai]

@JKSH I have the same problem and use CMake , what can I do?

[Christian Ehrlicher]

@david-azolai said in Undefined reference to staticMetaObject:

I have the same problem and use CMake , what can I do?

Show your CMakeLists.txt and describe exactly what you're doing / trying to do.