Александр Ананьев

class ContactsModel: public QAbstractListModel
{
    Q_OBJECT

public:
    explicit ContactsModel(const QVector<Contact>& items, QObject* parent = nullptr)
               : QAbstractListModel(parent)
                _items(items)
   {
   }

    int rowCount(const QModelIndex& parent = QModelIndex()) const override
    {
           return _items.size();
    }
    QVariant data(const QModelIndex& index, int role) const override
    {
    if(!index.isValid() ||
        index.row() < 0  ||
        index.row() >= _items.size())
    {
         return QVariant();
    }

    switch(role)
    {
        case Qt::DisplayRole:
           ...
    }

    return QVariant();
    }

private:
    QVector<Contact> _items;
};

import QtQuick.Controls 2.0
import QtQuick.Controls 1.4 as QQC1

Button {} //QQC2 button
QQC1.TreeView{} // QQC1 tree view