Question

I have a QComboBox so the user can a network name from from a model column. I’m using code like this:

self.networkSelectionCombo = QtGui.QComboBox()
self.networkSelectionCombo.setModel(self.model.worldLinks)
self.networkSelectionCombo.setModelColumn(WLM.NET_NAME)

I’m using PySide, but this is realy a Qt question. Answers using C++ are fine.

I need to give the user the option of not selecting any network. What I’d like to do is add an extra item to the combo box called ‘None’. However this will just get overridden by the model contents.

The only way I can think of is to create an intermediate custom view on this model column and use that to update the combo, then the view can handle adding in the extra ‘magic’ item. Does anyone know a more elegant way of doing this?

Answer 1

One possible solution is to subclass the model you are using in order to add there the extra item. The implementation is straight forward. If you call your model MyModel then the subclass would look like this (C++ used):

class MyModelWithNoneEntry : public MyModel
{
public:
    int rowCount() {return MyModel::rowCount()+1;}
    int columnCount() {return MyModel::columnCOunt();}
    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const
    {
        if (index.row() == 0)
        {
             // if we are at the desired column return the None item
             if (index.column() ==  NET_NAME && role == Qt::DisplayRole)
                  return QVariant("None");
             // otherwise a non valid QVariant
             else
                  return QVariant();
        }
        // Return the parent's data
        else
            return MyModel::data(createIndex(index.row()-1,index.col()), role);       
    } 

    // parent and index should be defined as well but their implementation is straight
    // forward
} 

Now you can set this model to the combo box.