How to map a multi-level object model with a QAbstractItemModel - c++

Question

I start to lern MVC pattern in Qt.
I have the simple data structure, like this:
class Stage
{
public:
QString name;
int number;
};
class Doc
{
public:
Doc();
~Doc();
QString name;
int number;
QList<Stage *> *stages;
};
I want to view this structure in TreeView. For this i create model class:
class Model: public QAbstractItemModel
{
Q_OBJECT
public:
Model(QObject *parent);
~Model();
QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;
QModelIndex index(int row, int column, const QModelIndex &parent) const;
QModelIndex parent(const QModelIndex &index) const;
int rowCount(const QModelIndex &parent = QModelIndex()) const;
int columnCount(const QModelIndex &parent = QModelIndex()) const;
Qt::ItemFlags flags(const QModelIndex &index) const;
QVariant headerData(int section, Qt::Orientation orientation,
int role = Qt::DisplayRole) const;
private:
QList<Doc*> *docs;
If I have only one level of data (doc without stage), everything works fine, but I can't understand how to add second tree level to the model(stage)?
Code example (one level)
Model::Model(QObject *parent) : QAbstractItemModel(parent)
{
docs = new QList<Doc*>();
for (int i = 0; i < 3; ++i) {
Doc *d = new Doc();
d->name = "name_" + QString::number(i);
d->number = i;
docs->append(d);
}
}
Model::~Model()
{
delete docs;
}
QModelIndex Model::index(int row, int column, const QModelIndex &parent) const
{
if (!parent.isValid()) {
Doc *d = docs->at(row);
return createIndex(row, column, d);
}
return QModelIndex();
}
QModelIndex Model::parent(const QModelIndex &index) const
{
return QModelIndex();
}
int Model::rowCount(const QModelIndex &parent) const
{
int cnt = 0;
if (!parent.isValid()) {
cnt = docs->size();
}
return cnt;
}
int Model::columnCount(const QModelIndex &parent) const
{
Q_UNUSED(parent);
return 3;
}
Qt::ItemFlags Model::flags(const QModelIndex &index) const
{
if (!index.isValid())
return nullptr;
return Qt::ItemIsEnabled | Qt::ItemIsSelectable;
}
QVariant Model::headerData(int section, Qt::Orientation orientation, int role) const
{
if (role != Qt::DisplayRole)
return QVariant();
if (orientation == Qt::Horizontal) {
switch (section) {
case 0:
return tr("Number");
case 1:
return tr("Code");
case 2:
return tr("Stages count");
default:
return QVariant();
}
}
return QVariant();
}
QVariant Model::data(const QModelIndex &index, int role) const
{
if (!index.isValid())
return QVariant();
if (role != Qt::DisplayRole)
return QVariant();
{
Doc *d = static_cast<Doc*>(index.internalPointer());
switch (index.column()) {
case 0:
return d->name;
case 1:
return d->number;
case 2:
return d->stages->size();
default:
break;
}
}
return QVariant();
}
i think its will look like this:
Model::Model(QObject *parent) : QAbstractItemModel(parent)
{
docs = new QList<Doc*>();
for (int i = 0; i < 3; ++i) {
Doc *d = new Doc();
d->name = "name_" + QString::number(i);
d->number = i;
for (int j = 5; j < 9; ++j) {
Stage *s = new Stage();
s->name = "name_" + QString::number(j);
s->number = j;
d->stages->append(s);
}
docs->append(d);
}
}
QModelIndex Model::index(int row, int column, const QModelIndex &parent) const
{
if (!parent.isValid()) {
Doc *d = docs->at(row);
return createIndex(row, column, d);
} else {
Stage *s = static_cast<Doc*>(parent.internalPointer())->stages->at(row);
return createIndex(row, column, s);
}
return QModelIndex();
}
QModelIndex Model::parent(const QModelIndex &index) const
{
if (!index.isValid())
return QModelIndex();
else if (index.parent().isValid())
return createIndex(index.parent().row(), 0, index.internalPointer());
return QModelIndex();
}
int Model::rowCount(const QModelIndex &parent) const
{
int cnt = 0;
if (!parent.isValid()) {
cnt = docs->size();
} else {
cnt = static_cast<Doc*>(parent.parent().internalPointer())->stages->size();
}
return cnt;
}
but its wrong code...