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# model.cpp Example File
demos/interview/model.cpp

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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
     {
         return (parent.isValid() && parent.column() != 0) ? 0 : rc;
     }

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

     QVariant Model::data(const QModelIndex &index, int role) const
     {
         if (!index.isValid())
             return QVariant();
         if (role == Qt::DisplayRole)
             return "Item " + QString::number(index.row()) + ":" + QString::number(index.column());
         if (role == Qt::DecorationRole) {
             if (index.column() == 0)
                 return iconProvider.icon(QFileIconProvider::Folder);
             return iconProvider.icon(QFileIconProvider::File);
         }
         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
     {
         if (parent.isValid() && parent.column() != 0)
             return false;
         return rc > 0 && cc > 0;
     }

     Qt::ItemFlags Model::flags(const QModelIndex &index) const
     {
         if (!index.isValid())
             return 0;
         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);
     }