How to send JS object to QML from C++

[Vlados]

Hello everyone! I couldn't find answer to my question. I want to draw a some MapPolyLine on Map, but I get data from model using QSQLQueryModel.

class TracksModel : public QSqlQueryModel
{
    Q_OBJECT
public:
    enum Roles {
        IdRole = Qt::UserRole + 1,
        NameRole,
        PointsRole
    };

    explicit TracksModel(QObject *parent = 0);
    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;

protected:
    QVector<QVariantList> tracks;
    QHash<int, QByteArray> roleNames() const;
    QVector<QVariantList>  getPointsOfTracks();

signals:

public slots:
    void updateModel();
    int getId(int row);
};

I need that all points of a single track contained in model.points. I use it in QML:

MapItemView{
        id: tracksLines
        model: tracksModel
        delegate: MapPolyline {
            line.width: 3
            line.color: 'blue'
            path: tracksModel.points
        }
    }

But, It Doesn't work. Ok, I tested next code:

MapItemView{
        id: tracksLines
        model: tracksModel
        delegate:
            MapPolyline {
            line.width: 3
            line.color: 'red'
            path: [
                { latitude: points[0].latitude, longitude: points[0].longtitude},
                { latitude: points[1].latitude, longitude: points[1].longtitude}
            ]
        }
    }

And It works! But I don't know how many points will be in the "poinst" and I don't know how many tracks therefore I use the model. My data is stored in the database.

Now let's move to c++.
It's short tracksmodel.cpp:

QVariant TracksModel::data(const QModelIndex & index, int role) const {
    if (role == PointsRole)
    {
        return tracks[index.row()];
    }

    int columnId = role - Qt::UserRole - 1;
    QModelIndex modelIndex = this->index(index.row(), columnId);
    return QSqlQueryModel::data(modelIndex, Qt::DisplayRole);
}

QHash<int, QByteArray> TracksModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[IdRole] = "id";
    roles[NameRole] = "name";
    roles[PointsRole] = "points";
    return roles;
}

void TracksModel::updateModel()
{
    this->tracks = this->getPointsOfTracks();
    QString str_query("SELECT id, name FROM Tracks;");
    this->setQuery(str_query);
    qDebug() << str_query << endl;
    qDebug() << this->tracks[0][0] << endl;
}

QVector<QVariantList> TracksModel::getPointsOfTracks()
{
    QVector<QVariantList> temp_tracks;
    for (int i = 0; i <= 3; i++) // обрабатываем каждый трек
    {
       // 2 constant points for expirement
       QVariantList path;
       QVariantMap point;
       point["latitude"] = QVariant(55.928848 + (0.000680 * i));
       point["longtitude"] = QVariant(37.519537 + (0.002200 * i));
       path.append(point);
      
       QVariantMap point2;
       point2["latitude"] = QVariant(55.928169 + (0.000680 * i));
       point2["longtitude"] = QVariant(37.521683 + (0.002200 * i));
       path.append(point2);
       temp_tracks.push_back(path);
    }
    return temp_tracks;
}

In general, how to draw MapPolyLine with C++ data?
Thank you in advance!
P.S.Sorry for Google translator.

[Vlados]

I have found that the function processes the data: http://code.qt.io/cgit/qt/qtlocation.git/tree/src/imports/location/qdeclarativepolylinemapitem.cpp#n525 . I get error "QML MapPolyline: Unsupported path type" when I set path. I'm trying to send an QJSValue, but I receive an error.