Unresolved external symbol "public: virtual struct QMetaObject const * __thiscall Parent

Question

I inherited a class from QObject :

class Parent: public QObject
{
    Q_OBJECT
    QObject* cl;

public:
    Parent(QObject *parent=0):QObject(parent) {
            


        

Answer 1

I solved my problem by adding this to my header file :

#ifndef MYCLASSNAME_H
#define MYCLASSNAME_H

... // all the header file content.

#endif

Answer 2

I know that this is a very old question, but it seems to be still interesting (I've been here at least 4 or 5 times in the last months) and seems like I found another reason for which is possible to get this error.

In my case in the header file I wrongly typed:

#include "MyClass.h""

Only after inspecting the whole output I found out that at that line the compiler was emitting a warning.

Now that I removed the additional quotation mark my QObject compiles perfectly!

Answer 3

If you're using Visual Studio, delete the line Q_OBJECT from the header file, save the file, put Q_OBJECT back into the header file, save the file again. This should generate the moc_* file and should build and link correctly.

Answer 4

So the issue was I needed the Qt MOC compiler to compile my .h file. This is required for any classes that extend QObject or one of its children. The fix involed (for me) right-clicking on the header file, choosing Properties, and setting the Item Type to "Qt MOC Input", then hitting "Compile" on the header, and then adding the resulting moc_myfilename.cpp file to my project.

Answer 5

For me, this is the cause: some header or source file not included in QT's project file

Answer 6

I have the same problem, my solution was the encoding( my file with "UTF16LE BOM" can't generate with moc.exe ) , y create another file with ASCII enconding and it work.

HxD HexEditor can help you to see the codification.