How to send JS object to QML from C++

  • 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
        enum Roles {
            IdRole = Qt::UserRole + 1,
        explicit TracksModel(QObject *parent = 0);
        QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
        QVector<QVariantList> tracks;
        QHash<int, QByteArray> roleNames() const;
        QVector<QVariantList>  getPointsOfTracks();
    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:

            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:

            id: tracksLines
            model: tracksModel
                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;");
        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));
           QVariantMap point2;
           point2["latitude"] = QVariant(55.928169 + (0.000680 * i));
           point2["longtitude"] = QVariant(37.521683 + (0.002200 * i));
        return temp_tracks;

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

  • I have found that the function processes the data: . I get error "QML MapPolyline: Unsupported path type" when I set path. I'm trying to send an QJSValue, but I receive an error.

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