Proxy model example code

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Related to "this FAQ entry":http://developer.qt.nokia.com/faq/answer/how_can_i_implement_my_own_proxy_model_that_is_more_advanced_than_just_sort.


#include <QtGui&gt;

QList&lt;QStandardItem *> list;

class SortProxy : public QAbstractProxyModel
{
Q_OBJECT

public:
SortProxy(QObject *parent = 0) : QAbstractProxyModel(parent), hideThem(false)
{
fixModel();
}

int rowCount(const QModelIndex &parent) const
{
QModelIndex sourceParent;
if (parent.isValid())
sourceParent = mapToSource(parent);
int count = 0;
QMapIterator&lt;QPersistentModelIndex, QPersistentModelIndex&gt; it(proxySourceParent);
while (it.hasNext()) {
it.next();
if (it.value() == sourceParent)
count++;
}
return count;
}

int columnCount(const QModelIndex &) const
{
return 1;
}

QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const
{
QModelIndex sourceParent;
if (parent.isValid())
sourceParent = mapToSource(parent);
QMapIterator&lt;QPersistentModelIndex, QPersistentModelIndex&gt; it(proxySourceParent);
while (it.hasNext()) {
it.next();
if (it.value() sourceParent &amp;&amp; it.key().row() row &&
it.key().column() == column)
return it.key();
}
return QModelIndex();
}

QModelIndex parent(const QModelIndex &child) const
{
QModelIndex mi = proxySourceParent.value(child);
if (mi.isValid())
return mapFromSource(mi);
return QModelIndex();
}

QModelIndex mapToSource(const QModelIndex &proxyIndex) const
{
if (!proxyIndex.isValid())
return QModelIndex();
return mapping.key(proxyIndex);
}

QModelIndex mapFromSource(const QModelIndex &sourceIndex) const
{
if (!sourceIndex.isValid())
return QModelIndex();
return mapping.value(sourceIndex);
}

public slots:
void hideEverythingButA1AndChildren()
{
hideThem = !hideThem;
// Now we set up the proxy <> source mappings
emit layoutAboutToBeChanged();
fixModel();
emit layoutChanged();
}
private:
void fixModel()
{
mapping.clear();
proxySourceParent.clear();
for (int i=0;i&lt;list.size();i+) {
QStandardItem *si = list.at(i);
if (hideThem) {
if (!si->text().startsWith("A&quot;) || !si->parent())
continue;
QModelIndex proxy = createIndex(si->row(), si->column(), si->index().internalPointer());
mapping.insert(QPersistentModelIndex(si->index()), proxy);
QModelIndex sourceParent;
if (si->parent()>parent())
sourceParent = si
>parent()>index();
proxySourceParent.insert(proxy, sourceParent);
} else {
QModelIndex proxy = createIndex(si
>row(), si->column(), si->index().internalPointer());
mapping.insert(QPersistentModelIndex(si->index()), proxy);
QModelIndex sourceParent;
if (si->parent())
sourceParent = si->parent()>index();
proxySourceParent.insert(proxy, sourceParent);
}
}
}
QMap&lt;QPersistentModelIndex, QPersistentModelIndex&gt; mapping;
QMap&lt;QPersistentModelIndex, QPersistentModelIndex&gt; proxySourceParent;
bool hideThem;
};

SortProxy *proxyModel = 0;
class Tree : public QTreeView
{
Q_OBJECT
public:
Tree(QWidget *parent = 0) : QTreeView(parent)
{
QStandardItemModel *sourceModel = new QStandardItemModel(this);
QStandardItem *parentA = sourceModel
>invisibleRootItem();
for (int i = 0; i < 2;i) {
itemA = new QStandardItem(QString("A %0&quot;).arg(i));
parentA->appendRow(itemA);
parentA = itemA;
list.append(itemA);
}
itemA = new QStandardItem(QString("A 2&quot;));
parentA->appendRow(itemA);
list.append(itemA);
itemA3 = new QStandardItem(QString("A 3&quot;));
list.append(itemA3);
parentA->appendRow(itemA3);
itemA4 = new QStandardItem(QString("A 4&quot;));
list.append(itemA4);
parentA->appendRow(itemA4);
itemNonA = new QStandardItem(QString("Non A&quot;));
list.append(itemNonA);
parentA->appendRow(itemNonA);
QStandardItem *parentB = sourceModel->invisibleRootItem();
for (int i = 0; i < 3;i) {
itemB = new QStandardItem(QString("B %0&quot;).arg(i));
parentB->appendRow(itemB);
parentB = itemB;
list.append(itemB);
}
QStandardItem *parentC = sourceModel->invisibleRootItem();
for (int i = 0; i < 3;i) {
itemC = new QStandardItem(QString("C %0&quot;).arg(i));
parentC->appendRow(itemC);
parentC = itemC;
list.append(itemC);
}
proxyModel = new SortProxy(this);
proxyModel->setSourceModel(sourceModel);
setModel(proxyModel);
expandAll();
}
QStandardItem *itemA;
QStandardItem *itemA3;
QStandardItem *itemA4;
QStandardItem *itemNonA;
QStandardItem *itemB;
QStandardItem itemC;
};


#include "main.moc&quot;
int main(int argc, char'*argv)
{
QApplication app(argc, argv);
QWidget widget;
QPushButton *button = new QPushButton("Make only A1
'A' children visible&quot;, &widget);
Tree *tree = new Tree(&widget);
QVBoxLayout *lay = new QVBoxLayout(&widget);
lay
>addWidget(button);
QObject::connect(button, SIGNAL (clicked()), proxyModel, SLOT (hideEverythingButA1AndChildren()));
lay->addWidget(tree);
widget.show();
return app.exec&amp;#40;&#41;;
}