I want to display a subset of columns from an large existing C++ TableModel in a new QML TableView.
All the documenation and examples I've read override QAbstractItemModel::roleNames() to expose model data associated with the roles as properties in QML.
The problem is that the legacy TableModel's data() function has a complex implementation tightly coupled to Qt::DisplayRole:
\\...
QVariant LegacyModel::data(const QModelIndex& index, int role) {
switch(role) {
\\...
case Qt::DisplayRole:
switch(LegacyTableColumn.at(index.column())) {
\\ lots of stuff
}
}
\\...
}
\\...
As such, I'd prefer to avoid overriding QAbstractItemModel::roleNames() as it will mean substantial refactoring of the above data() function.
I have a QML view showing all the columns in each model row:
TableView {
anchors.fill: parent
model: LegacyModel
delegate: RowLayout {
implicitWidth: parent.width
Text {
text: model.display // i.e., inferred from Qt::DisplayRole
// can I access column data here somehow?
}
}
}
But I only want to display a small set of columns.
Is there a way to do that without overriding roleNames() and using those as properties in the view?
As far as I can tell it looks like the only way to avoid custom roles is to hack a Q_INVOKABLE function in the model:
// LegacyModel.h:
...
Q_INVOKABLE QVariant getMyData(int row, int column) const { return m_data[row][column]; }
...
// TableView.qml:
TableView {
...
model: LegacyModel
delegate: RowLayout {
...
Text {
text: model.getMyData(row, 2)
}
Text {
text: model.getMyData(row, 5)
}
// etc.
}
}
Not a great solution, so I'm going to create a new model with custom roles insted.
Related:
How to implement QML ListModel like get method for an QAbstractListModel derived model