Proper way to add enum class to metaObject Qt 5.15 - c++

Question

I'm tinkering a bit with Qt's meta-object system, and I've come across an issue with adding enum class to a meta-object. I have a struct that contain some variables, one of which is an enum class.
#ifndef EXAMPLE_H
#define EXAMPLE_H
#include <QObject>
enum class CarType {
NO_CAR = 0,
SLOW_CAR,
FAST_CAR,
HYPER_CAR
};
struct Player {
Q_GADGET
Q_PROPERTY(Player player READ getPlayer)
Q_PROPERTY(float m_speed READ getSpeed)
Q_PROPERTY(CarType m_carType READ getCarType)
Player getPlayer() { return *this;}
float getSpeed() {return m_speed;}
CarType getCarType() { return m_carType;}
public:
CarType m_carType;
float m_speed;
}; Q_DECLARE_METATYPE(Player)
#endif // EXAMPLE_H
I declare this struct as a Q_META_TYPE, in order to access it with the meta-object system. This allows me to access the struct's properties. Here is my main.cpp:
#include <QCoreApplication>
#include <iostream>
#include <QMetaObject>
#include "example.h"
#include <QDebug>
#include <QMetaProperty>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
qRegisterMetaType<Player>();
const QMetaObject* metaObject = &Player::staticMetaObject;
qInfo()<< "Number of enums is: " << metaObject->enumeratorCount();
return a.exec();
}
I expect that enumeratorCount() would be 1, however I get 0. I've searched about this issue, and most examples I could find have the struct inside a class, and the Q_ENUM declaration right after it, like this:
enum class CarType {
NO_CAR = 0,
SLOW_CAR,
FAST_CAR,
HYPER_CAR
}; Q_ENUM(CarType)
This, however, results in an error. What's the proper way to register this enum in the meta-object system?
Thanks for your time.
EDIT
The errors that I get that are relevant are:
/home/raphael/SO_Example/example.h:10: error: ‘friend’ used outside of class
/home/raphael/SO_Example/example.h:10: error: ‘staticMetaObject’ was not declared in this scope; did you mean ‘qt_getQtMetaObject’?

Answer 1

If you don't want to add your enum to a class with Q_OBJECT or Q_GADGET, then the other way to do it is to put your enum inside a Q_NAMESPACE. You can't actually use Q_ENUM with Q_NAMESPACE, but you can use Q_ENUM_NS instead. I haven't tested this myself, but it should work:
namespace MyNamespace
{
Q_NAMESPACE
enum class MyEnum {
Foo,
Bar
};
Q_ENUM_NS(MyEnum)
}