Proper way to add enum class to meta-object Qt 5.15

raphasauer

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. My goal is to access this enum through metaObject.enumerator(). Here is my code:

#ifndef EXAMPLE_H
#define EXAMPLE_H
#include <QObject>

//Make this enum class accessible through the struct Player
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)

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();
}

Currently, metaObject->enumeratorCount() returns 0. Is there a way to make that enum class accessible in main.cpp through Player's metaObject?

mrjj

Hi
It hink you might have to register the actual enum as they do here
https://forum.qt.io/topic/41032/solved-enum-class-with-qvariant-how-to-register-strongly-typed-enum-with-qt-meta-system

raven-worx

@raphasauer
i dont think that you can register global enum through a Q_GADGET/Q_OBJECT.

But you can declare a namespace in which the enum resides:

namespace MyNamespace
{
    Q_NAMESPACE
 
    enum class MyEnum {
        Foo,
        Bar
    };
    Q_ENUM_NS(MyEnum)
}

raphasauer

@mrjj and @raven-worx , thanks for the replies! What I've gathered from this (and other posts) is: you can't use a Q_ENUM outside of QObject or a Q_GADGET macro. So in order to do what I wanted I need to change the code like this:

#ifndef EXAMPLE_H
#define EXAMPLE_H
#include <QObject>

struct Player {
    Q_GADGET

public:
    enum class CarType {
        NO_CAR = 0,
        SLOW_CAR,
        FAST_CAR,
        HYPER_CAR
    }; Q_ENUM(CarType)

    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

#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();
    const QMetaEnum metaEnum = metaObject->enumerator(0);
    qInfo() << "Enum name: " << metaEnum.enumName();
    int i = 0;
    for(i = 0; i < metaEnum.keyCount(); i++)
        qInfo() << "Enum key: " << metaEnum.key(i) << "; Value: " << metaEnum.value(i);
    return a.exec();
}

Thanks for your time!