QFlags is only usable on enumeration types

medihe

Hi,

I would like to ask you about an error with QFlag.

The following sentence in qt4 compiles:

QTreeWidgetItem *item  = new QTreeWidgetItem;
QFlags<Qt::ItemFlags> flags (item->flags() );

However, compiling with qt5 it shows the error:
qtcore\qflags.h(96): error C2338: QFlags is only usable on enumeration types

Apparently this error is because of an assert:
Q_STATIC_ASSERT_X((std::is_enum<Enum>::value), "QFlags is only usable on enumeration types.");

But, Qt::ItemFlags is an defined user type:

enum ItemFlag {
        NoItemFlags = 0,
        ItemIsSelectable = 1,
        ItemIsEditable = 2,
        ItemIsDragEnabled = 4,
        ItemIsDropEnabled = 8,
        ItemIsUserCheckable = 16,
        ItemIsEnabled = 32,
        ItemIsAutoTristate = 64,
#if QT_DEPRECATED_SINCE(5, 6)
        ItemIsTristate = ItemIsAutoTristate,
#endif
        ItemNeverHasChildren = 128,
        ItemIsUserTristate = 256
    };
    Q_DECLARE_FLAGS(ItemFlags, ItemFlag)

So from my understanding it should work. Anyway, it seems it compiles using "Qt::ItemFlag" instead of "Qt::ItemFlags".

QTreeWidgetItem *item  = new QTreeWidgetItem;
QFlags<Qt::ItemFlags> flags (item->flags() );

However, someone could please explain why it is happening in qt and it is the right solution?

Thanks in advance.

[edit:koahnig, code tags added]

kshegunov

That's because Qt::ItemFlags is already a typedef for QFlags<Qt::ItemFlag>, meaning you can and should use it like this:

Qt::ItemFlags flags = item->flags();

medihe

That is right.

Thank you very much for your help.