QComboBox::findData fails when QVariant stores a std::vector

Question

Consider this code:

std::vector< std::vector<int> > v;
v.push_back( std::vector<int>( 1, 4 ) );
v.push_back( std::vector<int>( 1, 3 ) );
QComboBox box;
box.addItem( "", QVariant::fromValue<std::vector<int>>( v[0] ) );
box.addItem( "", QVariant::fromValue<std::vector<int>>( v[1] ) );
int pos = box.findData( QVariant::fromValue<std::vector<int>>(v[0]) );

pos is -1, when 0 was expected.

Manual search (for i to box.count()) is doable and works. As ( box.itemData( 0 ).value< std::vector<int> >() == v[0] ) surprisingly returns true! But findData is supposed to work too!

Note: Adding Q_DECLARE_METATYPE( std::vector<int> ); did not help

Edit 2016/05/03: Filled a Qt bug: https://bugreports.qt.io/browse/QTBUG-53152

Have you tried using a type other than `A`, such as `int`? This will isolate if the problem is with `A` or `std::vector`. — jonspaceharper, Apr 29 '16 at 14:21
@JonHarper: Good point. Same problem with `int*`, so apparently the problem comes from `std::vector` — jpo38, Apr 29 '16 at 14:44
@JonHarper: See last Note in my post, already tried that. Had no effect. — jpo38, Apr 29 '16 at 14:51
My answer was completely wrong. `std::vector` is declared by default with [`Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE`](http://doc.qt.io/qt-5/qmetatype.html#Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE) — jonspaceharper, Apr 29 '16 at 19:54

score 4 · Accepted Answer · answered May 09 '16 at 08:05

4

QMetaType::registerComparators has to be called to have operator== be used instead of bitwise comparison.

Calling (once): QMetaType::registerComparators<std::vector<int>>(); makes findData work.

answered May 09 '16 at 08:05

jpo38

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QComboBox::findData fails when QVariant stores a std::vector

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