Q_ENUM and typedef

jsulm

Hi!
I would like to use Q_ENUM with a typedef like bellow:

class TestEnum
{
    Q_GADGET
public:
    TestEnum();

    typedef enum SomeEnum_
    {
        value1,
        value2,
        value3
    } SomeEnum;
    Q_ENUM(SomeEnum)

    void printEnum(SomeEnum value)
    {
        qDebug() << Q_FUNC_INFO;

        QMetaEnum metaEnum = QMetaEnum::fromType<SomeEnum>();
        qDebug() << metaEnum.isValid();
        qDebug() << "Key" << metaEnum.key(value);
    }
};

Without typedef it works as expected (the key name is printed). But with typedef it does not work and metaEnum.isValid() returns false. Is there a way to use Q_ENUM with enums declared using typedef?
The reason why I would like to use typedef is that we give our own names to enums provided by the supplier using typedef.

kshegunov

@jsulm
Hi,
If you're willing to live with the Q_ENUM macro referencing the non-aliased type, the QMetaEnum::fromType function will work as expected. I.e.:

class TestEnum
{
    typedef enum SomeEnum_
    {
    } SomeEnum;
    Q_ENUM(SomeEnum_) //< No alias for the macro

    void printEnum(SomeEnum value)
    {
        QMetaEnum metaEnum = QMetaEnum::fromType<SomeEnum>(); //< Works okay
    }
};

But I think you can't use a typedef-ed enum with the macro. If I'm not mistaken there's no way to deduce the corresponding meta-object this way, and consequently it doesn't work.

jsulm

The Q_ENUMS macro works with typedefs.

kshegunov

@jsulm
Yes, but the new macro is "smart" ... Here's a good article dealing with it, if you haven't stumbled on it, I suggest taking a quick look. If I had to guess what the problem is, I'd say it's the overloading rules that are confused, which is always a danger when working with templates. Most probably the trick with SFINAE they're using doesn't go well with aliased enums.
I'm not that well versed in the internals, though, so I might simply be wrong.

PS.
You might get a more coherent answer on the mailing list.

Kind regards.