QAbstractTableModel retrieve custom object on data changed - c++

Question

I have recently picked up Qt again, and started refreshing my memory.
Creating a custom data model for a table was easy enough.
Now I am trying to retrieve the selected data.
Take note that I use custom data objects.
Example of my custom model:
platform.h
class Platform
{
public:
Platform();
Platform(QString name);
QString getName();
void setName(QString name);
private:
QString m_name;
};
Very simple data structure for testing purposes.
I then implemented a QAbstractTableModel, the Data() method looks like this:
platformmodel.cpp
QVariant PlatformModel::data(const QModelIndex &index, int role) const
{
if (!index.isValid())
return QVariant();
if (index.row() >= m_platforms.size() || index.row() < 0)
return QVariant();
if (role == Qt::DisplayRole) {
Platform platform = m_platforms.at(index.row());
qDebug() << platform.getName();
return platform.getName();
}
return QVariant();
}
What I understand from this code is, that for the selectable items, a String is always returned, instead of a platform object.
For displaying, this works fine, I see the actual objects in the view.
Now I want to select the actual object from the model, and not just a QString.
So the method body would be something like:
void MainWindow::selectionChangedSlot(const QItemSelection &, const QItemSelection &)
{
//get the text of the selected item
const QModelIndex index = ui->lvPlatforms->selectionModel()->currentIndex();
Platform selectedPlatform = index.data();//This returns a QVariant and will fail at compile time, but I want to achieve something along this line.
setWindowTitle(selectedPlatform.getName());
}
P.s. Maybe I am trying to search on the wrong thing, I can find examples that use custom objects, but none talk about retrieving the selected item.
There has to be a better way then retreiving the string, then looping trough the list of platforms and comparing the name to the selected item.. If i have a big list, having to loop trough each item and do string comparison is not very efficient.
I hope my problem is clear enough. If something important lacks, let me know so I can edit my example.
EDIT
I tried Q_DECLARE_METATYPE(Platform);
And yes it works, it makes it possible to store it in a QVariant,
the problem is, since for displaying, a String is always expected, or 9/10 times anyway.
So far it seems impossible to have both text display AND get the full platform object from the selection model(i can do both individually.. pretty useless..)

Answer 1

You can create custom type compatible with QVariant using the macro Q_DECLARE_METATYPE.
If you declare your class as a metatype, you can store it in a QVariant and extract it with a cast.
Here an example that show how to create a custom delegate which can display data from a custom class using QVariant :
class Data {
private:
QString name;
int value;
public:
Data() : name(""), value(-1){}
Data( QString n, int v ) : name(n), value(v){}
QString text() {
return QString( "Test %1 - %2" ).arg( name ).arg( value );
}
};
Q_DECLARE_METATYPE( Data )
class Delegate : public QStyledItemDelegate {
protected:
void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const {
Data d = index.data().value<Data>();
painter->drawText( option.rect, d.text() );
}
};
int main( int argc, char **argv) {
QApplication app(argc, argv, true);
QVariant var0, var1, var2;
var0.setValue(Data( "Item A", 0 ));
var1.setValue(Data( "Item B", 1 ));
var2.setValue(Data( "Item C", 2 ));
QListView *view = new QListView();
QStandardItemModel model(3, 1);
model.setData( model.index( 0, 0 ), var0 );
model.setData( model.index( 1, 0 ), var1 );
model.setData( model.index( 2, 0 ), var2 );
view->setModel( &model );
view->show();
view->setItemDelegate( new Delegate() );
return app.exec();
}