Filling QML ListView with data from std::map - c++

Question

I'm having trouble finding a good way to display the items of a std::map in QML. We're using a MVVM pattern in our application. The std::map contains file paths and is a member of a configuration class in the model.
Now I'm trying to show all entries of the map in QML, probably using a ListView item.
Currently we just have a couple of file paths in the configuration, so these are exposed as Q_PROPERTYies to the view model and then further to QML. But, of course, the number of paths can and will grow, thus my idea using a std::map for this. It won't be necessary to have it 'growable' at runtime, at least not in the forseeable future. But writing lots and lots of Q_PROPERTYies doesn't seem the right way for me.
Furhter question: How would I access/display the items of the map in a QML ListView - I can't figure it out and I can't find anything helpful online.

Answer 1

Another option than #ddriver suggested would be to create a list of QObject-derived types like:
class ConfigObject: public QObject
{
Q_PROPERTY(QString key READ key)
Q_PROPERTY(QString value READ value)
// ... getters and key and value members
};
fill a QList with them and provide them as a model for ListView either via
QVariantList configModel;
// ... fill it with ConfigObjects from std::map
engine.rootContext()->setContextProperty("configModel", &configModel); //QQmlApplicationEngine here
or a property of some class:
Q_PROPERTY(QVariant configModel READ configModel NOTIFY configModelChanged)
Then you should be able to use it via modelData.key and modelData.value in your ListView delegate.
ListView {
model: configModel // in case of using context
delegate: Item {
...
Text {
text: modelData.key
}
Text {
text: modelData.value
}
}
}

Answer 2

You should implement a model adapter for std::map by extending a QAbstractListModel, then you can use that as the model for a QML ListView. Implementing the right set of model roles will allow you to access the map element members without the need to use Q_PROPERTY which also requires a QObject derived datatype. Then you only need to expose the model to QML, as a context property for example.
Keep in mind the map is a sorted container, so if you modify the model you should properly reflect the index of insertion and deletion.
So you will have:
std::map -> YourCustomListModel -> ListView