Q_ENUM(enum_name) works with only enums declared inside class. srsly?

Kofr

Let's look at example from documentation which is copied next.

class Message : public QObject
 {
     Q_OBJECT
     Q_ENUMS(Status)
     Q_PROPERTY(Status status READ status NOTIFY statusChanged)
 public:
     enum Status {
         Ready,
         Loading,
         Error
     };
     Status status() const;
 signals:
     void statusChanged();
 };

In this example we declare our enumeration declared inside class with Q_ENUM(). It is ok. But what if we want to use Globally declared enumeration. Qt gives errors. How can we achieve operating with enumerations declared outside the class?

SGaist

Hi,

You can't, Q_ENUMS need a meta object provided either by the QObject class or the Q_GADGET macro

dethtoll

This is an old topic, but still comes up as one of the first Google results. I just wanted to add:

If the main goal is to use the enum as a property, it is sufficient to just use Q_DECLARE_METATYPE after the globally-declared enumeration.

If you need the other conveniences of Q_ENUM, then SGaist's reply applies.

raven-worx

@Kofr said in Q_ENUM(enum_name) works with only enums declared inside class. srsly?:

How can we achieve operating with enumerations declared outside the class?

This is possible since Qt 5.8 where the Q_NAMESPACE macro was introduced. This enables the generation of a MOC object also for namespaces.

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

Note the Q_ENUM_NS macro here. There is also a Q_FLAG_NS macro available.