Get all enum value names from C++ enum definition

SebastianM

Hi,
System spec: Windows 10, Qt 6.9, mingw64 13.10, Qt Creator 17.0.1
Classic C++ enum side declaration.

#include <QObject>
#include <QtQml/qqml.h>

class BackgroundType : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    QML_UNCREATABLE("BackgroundType is not creatable - use enum values only")

public:
    explicit BackgroundType(QObject *parent = nullptr) : QObject(parent) {}

    enum Value {
        Basic,
        Upper,
        VIP
    };
    Q_ENUM(Value)
};

This class is NOT compiled with qt_add_qml_module. So I used

    qmlRegisterUncreatableType<BackgroundType>("InfModule", 1, 0,
                                          "BackgroundType",
                                          "BackgroundTypeis not creatable - use enum values only");

Now, In QML side I would like to get list of all value names. For test purpose to scroll through them in combobox and check if all is fine.
Q_PROPERTY with static QStringList, Q_INVOKABLE returning QStringList - none of them work.
How to achive enum availabilty of uncreatable type with ability to print all enum values names?

SebastianM

Partial solution which I found is to register this enum C++ class as creatable.
Then in point where I need value names - is to call is JS section

var obj = Qt.createQmlObject('import InfModule1.0; BackgroundType {}', parent); 
obj.names();

Bob64

I don't know if there is a simpler way that is already built in, but you could look into using QMetaEnum on the C++ side and expose it to QML.

SebastianM

To be clear - I would like to call from QML side BackgroundType.getValueNames(); and receive QStringList("Basic", "Upper", "Vip").
Or my own QStrings mapping - like QStringList("Basic Background", "Upper Level Background", "Vip Ultimate Background").

PS:

    Q_INVOKABLE QStringList fun() { return {"Basic"), "Upper", "VIP"}; }

it doesn't matter if it's registered with qmlRegisterType or qmlRegisterUncreatableType or if I remove QML_UNCREATABLE from dla in results - QML engine warns with
TypeError: Property 'names' of object InfModule/BackgroundType is not a function

SebastianM

Partial solution which I found is to register this enum C++ class as creatable.
Then in point where I need value names - is to call is JS section

var obj = Qt.createQmlObject('import InfModule1.0; BackgroundType {}', parent); 
obj.names();

SebastianM

Other solution is ... to create attached properties

namespace MessageTypes {
    Q_NAMESPACE
    QML_ELEMENT

    enum class Type {
        None,
        SessionOpened,
        ConfigurationExternal,
        ConfigurationGet,
    };
    Q_ENUM_NS(Type)

    inline static const QMap<Type, QString>& typeToString() {
        static const QMap<Type, QString> map = {
            {Type::None, "None"},
            {Type::SessionOpened, "SessionOpened"},
            {Type::ConfigurationExternal, "configuration/external"},
            {Type::ConfigurationGet, "configuration/get"},
        };
        return map;
    }

    inline static const QMap<QString, Type>& stringToType() {
        static QMap<QString, Type> reverseMap = []() {
            QMap<QString, Type> map;
            for (auto it = MessageTypes::typeToString().cbegin();
                 it != MessageTypes::typeToString().cend(); ++it) {
                map.insert(it.value(), it.key());
            }
            return map;
        }();
        return reverseMap;
    }
}

// Attached object type - contains the utility methods
class MessageTypesAttached : public QObject
{
    Q_OBJECT
    QML_ANONYMOUS  // Not directly instantiable

public:
    explicit MessageTypesAttached(QObject *parent = nullptr)
        : QObject(parent)
    {}

    // Helper functions
    Q_INVOKABLE inline static QString toString(MessageTypes::Type type) {
        return MessageTypes::typeToString().value(type, QString());
    }

    Q_INVOKABLE inline static MessageTypes::Type fromString(const QString& str, MessageTypes::Type defaultValue = MessageTypes::Type::None) {
        return MessageTypes::stringToType().value(str, defaultValue);
    }

    Q_INVOKABLE inline static QStringList getAllTypesName() {    
            return MessageTypes::typeToString().values();    
    }
}  
    

// Attaching type - provides access to the attached object
class MessageTypesUtils : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    QML_UNCREATABLE("MessageTypesUtils is only for attached properties")
    QML_ATTACHED(MessageTypesAttached)

public:
    explicit MessageTypesUtils(QObject *parent = nullptr)
        : QObject(parent)
    {}

    // Required static method for attached properties
    static MessageTypesAttached *qmlAttachedProperties(QObject *object)
    {
        return new MessageTypesAttached(object);
    }
};