qt4 to qt5 porting of roleNames code

NotificationsModel::NotificationsModel(QObject *parent) :
QAbstractListModel(parent)
{
QHash<int, QByteArray> roles = roleNames();
roles[Qt::DisplayRole] = QByteArray("title");
roles[ObjectRole] = QByteArray("object");
roles[BodyRole] = QByteArray("body");
roles[CountRole] = QByteArray("count");
setRoleNames(roles);
}

//roleNames needs to be reimplemented

//in .h
public:
    virtual QHash<int, QByteArray> roleNames() const;
private:
    QHash<int, QByteArray> _roles;
//in .c
NotificationsModel::NotificationsModel(QObject *parent) :
    QAbstractListModel(parent)
{
    QHash<int, QByteArray> _roles = roleNames();
    _roles[Qt::DisplayRole] = QByteArray("title");
    _roles[ObjectRole] = QByteArray("object");
    _roles[BodyRole] = QByteArray("body");
    _roles[CountRole] = QByteArray("count");
}

QHash<int, QByteArray> NotificationsModel::roleNames() const
{
    return _roles;
}

//gets me
watchletsmodel.cpp:18:24: error: prototype for 'QHash<int, QByteArray> sowatch::WatchletsModel::roleNames()' does not match any in class 'sowatch::WatchletsModel'
watchletsmodel.h:26:36: error: candidate is: virtual QHash<int, QByteArray> sowatch::WatchletsModel::roleNames() const