Define a derived QObject class inside an anonymous namespace?

Question

I am working with Qt 5.7 (C ++).

Inside the cpp file of one class, I use an anonymous namespace to create a class (some utility), which I will use only in this file.

However, I got binding errors if the utility class is derived from the Qt class. I think the problem is in the Q_OBJECT macro, if I do not add it, I do not get errors. But in any derived Qt class, it is mandatory / recommended to have a Q_OBJECT macro.

How can i avoid this? Is there any other approach to have a utility class with a file area?

A simple example for displaying errors: the CMyClass class uses a utility class (called CUtility) that derives from QWidget.

Thank.

CMyClass.h

class CMyClass
{
public:
   CMyClass();
   void someMethod();
};

CMyClass.cpp

#include <QtWidgets>
#include "CMyClass.h"

namespace
{
   class CUtility : public QWidget
   {
      Q_OBJECT
   public:
      CUtility(QWidget *p_parent = 0) : QWidget(p_parent){qDebug() << "CUtility constructor";}
      void utilityMethod() {qDebug() << "This is CUtility::utilityMethod()";}
   };
}


CMyClass::CMyClass()
{
   qDebug() << "CMyClass constructor.";
}

void CMyClass::someMethod()
{
   qDebug() << "This is CMyClass::someMethod().";
   CUtility p_myUtil;
   p_myUtil.utilityMethod();
}

Errors:

LNK2001: "public: virtual struct QMetaObject const * __cdecl` ':: CUtility:: metaObject (void) const" (? metaObject @CUtility @? A0x27a8253c @@UEBAPEBUQMetaObject @@XZ)

LNK2001: "public: virtual void * __cdecl` ':: CUtility:: qt_metacast (char const *)" (? qt_metacast @CUtility @? A0x27a8253c @@UEAAPEAXPEBD @Z) sin resolver

LNK2001: "public: virtual int __cdecl` anonymous namespace ':: CUtility:: qt_metacall (enum QMetaObject:: Call, int, void * *)" (? qt_metacall @CUtility @? A0x27a8253c @@UEAAHW4Call @QMetaObject @@HPEAPEAX @Z) sin resolver

Answer 1

Q_OBJECT, , , ++, moc ( moc_CMyClass.cpp, ).

Q_OBJECT, , . , .

, @KubaOber, cpp . qmake moc cpp .

Answer 2

. .

, moc , . , moc. .cpp.

, Q_OBJECT foo.cpp, #include "foo.moc" . qmake . .

Utility , . "" : , . static, , , .

// main.cpp
#include <QObject>

namespace {
   class Utility : public QObject {
      Q_OBJECT
   public:
      Utility(QObject *parent = {});
   };
}

Utility::Utility(QObject *parent) : QObject(parent) {}

int main() {
  Utility utility;
}

#include "main.moc"