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model.cpp Example File
^{demos/interview/model.cpp}

    /****************************************************************************
    **
    ** Copyright (C) 2004-2006 Trolltech AS. All rights reserved.
    **
    ** This file is part of the documentation of the Qt Toolkit.
    **
    ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 as published by the Free Software Foundation
    ** and appearing in the file LICENSE.GPL included in the packaging of
    ** this file.  Please review the following information to ensure GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
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    **
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    ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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    ****************************************************************************/

    #include "model.h"
    #include <QIcon>
    #include <QPixmap>

    Model::Model(int rows, int columns, QObject *parent)
        : QAbstractItemModel(parent),
          rc(rows), cc(columns),
          tree(new QVector<Node>(rows, Node(0)))
    {

    }

    Model::~Model()
    {
        delete tree;
    }

    QModelIndex Model::index(int row, int column, const QModelIndex &parent) const
    {
        if (row < rc && row >= 0 && column < cc && column >= 0) {
            Node *p = static_cast<Node*>(parent.internalPointer());
            Node *n = node(row, p);
            if (n)
                return createIndex(row, column, n);
        }
        return QModelIndex();
    }

    QModelIndex Model::parent(const QModelIndex &child) const
    {
        if (child.isValid()) {
            Node *n = static_cast<Node*>(child.internalPointer());
            Node *p = parent(n);
            if (p)
                return createIndex(row(p), 0, p);
        }
        return QModelIndex();
    }

    int Model::rowCount(const QModelIndex &parent) const
    {
        Q_UNUSED(parent);
        return rc;
    }

    int Model::columnCount(const QModelIndex &parent) const
    {
        Q_UNUSED(parent);
        return cc;
    }

    QVariant Model::data(const QModelIndex &index, int role) const
    {
        static QIcon folder(QPixmap(":/images/folder.png"));

        if (role == Qt::DisplayRole)
            return "Item " + QString::number(index.row()) + ":" + QString::number(index.column());
        if (role == Qt::DecorationRole)
            return qVariantFromValue(folder);
        return QVariant();
    }

    QVariant Model::headerData(int section, Qt::Orientation orientation, int role) const
    {
        static QIcon services(QPixmap(":/images/services.png"));
        if (role == Qt::DisplayRole)
            return QString::number(section);
        if (role == Qt::DecorationRole)
            return qVariantFromValue(services);
        return QAbstractItemModel::headerData(section, orientation, role);
    }

    bool Model::hasChildren(const QModelIndex &parent) const
    {
        Q_UNUSED(parent);
        return rc > 0 && cc > 0;
    }

    Qt::ItemFlags Model::flags(const QModelIndex &) const
    {
        return (Qt::ItemIsDragEnabled|Qt::ItemIsSelectable|Qt::ItemIsEnabled);
    }

    Model::Node *Model::node(int row, Node *parent) const
    {
        if (parent && !parent->children)
            parent->children = new QVector<Node>(rc, Node(parent));
        QVector<Node> *v = parent ? parent->children : tree;
        return const_cast<Node*>(&(v->at(row)));
    }

    Model::Node *Model::parent(Node *child) const
    {
        return child ? child->parent : 0;
    }

    int Model::row(Node *node) const
    {
         const Node *first = node->parent ? &(node->parent->children->at(0)) : &(tree->at(0));
         return (node - first);
    }