[Solved] QVariant and enums

DSav

It seems that QVariant::value() won’t work correctly with enums. It’s of course possible to use this, but it looks like hacking:
@
QVariant variant = enumValue; // EnumType enumValue
// ...
EnumType anotherValue = static_cast<EnumType>(variant.toInt());
@
Is there a cute way to obtain enum value from QVariant using QVariant::value()?

loladiro

Did you declare the enum with "Q_DECLARE_METATYPE()":http://doc.qt.nokia.com/4.7/qmetatype.html#Q_DECLARE_METATYPE ? If that still doesn't work you could wrap the enum in a struct (I know that works)

DSav

Yes, I’ve definitely declared. Wrapping in a struct looks like a kind of hacking as well :)

loladiro

Consider the following example:
@

class Test2
{
public:
Test2() {}
enum Test { V1=100, V2, V3 };
};

Q_DECLARE_METATYPE(Test2::Test)

int main(int argc, char *argv[])
{
QVariant v1 = Test2::V1;
qDebug() << v1.toInt(0) << v1.valueTest2::Test();

QVariant v2 = qVariantFromValue(Test2::V1);
qDebug() << v2.toInt(0) << v2.value<Test2::Test>();
return 0;

}
@

The output is:
@100 0
0 100 @
Does that help?

DSav

Yes, that is helpful, thanks.

ViRuSTriNiTy

Hi,

one side note: when using Q_DECLARE_METATYPE() on an enum you define it as user type in the Qt meta system. The drawback is that e.g. QMetaProperty::isEnumType() won't work anymore because its now a user defined type. Qt designer won't accept it either.

lgeyer

Please elaborate.
@
class Test : public QObject
{
Q_OBJECT
Q_ENUMS(Value)
Q_PROPERTY(Value value READ value WRITE setValue)

public:
enum Value { valueA, valueB, valueC };

void setValue(Value value) { value_ = value; }
Value value() const { return value_; }

private:
Value value_;
};

Q_DECLARE_METATYPE(Test::Value)

qDebug() << Test().metaObject()->property(1).isEnumType(); // true
@

ViRuSTriNiTy

@Lukas: What do you mean by "Please elaborate"?

andre

It seems that Lukas is demonstrating with a small code snippet that the claim made by ViRuSTrNiTy is untrue.

bam80

[quote author="loladiro" date="1307893708"]Consider the following example:
@

class Test2
{
public:
Test2() {}
enum Test { V1=100, V2, V3 };
};

Q_DECLARE_METATYPE(Test2::Test)

int main(int argc, char *argv[])
{
QVariant v1 = Test2::V1;
qDebug() << v1.toInt(0) << v1.valueTest2::Test();

QVariant v2 = qVariantFromValue(Test2::V1);
qDebug() << v2.toInt(0) << v2.value<Test2::Test>();
return 0;

}
@
[/quote]

Thank you. The enum doesn't need to be wrapped in a class.
Following works:
@

#include <QtDebug>

enum Test { V1=100, V2, V3 };

Q_DECLARE_METATYPE(Test)

int main(int argc, char *argv[])
{
QVariant v1 = V1;
qDebug() << v1.toInt(0) << v1.value<Test>();

QVariant v2 = QVariant::fromValue(V1);
qDebug() << v2.toInt(0) << v2.value<Test>();

}
@