QSortFilterProxyModel Class Reference
[QtGui module]

Sorting

QTableView and QTreeView have a sortingEnabled property that controls whether the user can sort the view by clicking the view's horizontal header. For example:

         treeView->setSortingEnabled(true);

When this feature is on (the default is off), clicking on a header section sorts the items according to that column. By clicking repeatedly, the user can alternate between ascending and descending order.

Behind the scene, the view calls the sort() virtual function on the model to reorder the data in the model. To make your data sortable, you can either implement sort() in your model, or use a QSortFilterProxyModel to wrap your model -- QSortFilterProxyModel provides a generic sort() reimplementation that operates on the sortRole() (Qt::DisplayRole by default) of the items and that understands several data types, including int, QString, and QDateTime. For hierarchical models, sorting is applied recursively to all child items. String comparisons are case sensitive by default; this can be changed by setting the sortCaseSensitivity property.

Custom sorting behavior is achieved by subclassing QSortFilterProxyModel and reimplementing lessThan(), which is used to compare items. For example:

 bool MySortFilterProxyModel::lessThan(const QModelIndex &left,
                                       const QModelIndex &right) const
 {
     QVariant leftData = sourceModel()->data(left);
     QVariant rightData = sourceModel()->data(right);

     if (leftData.type() == QVariant::DateTime) {
         return leftData.toDateTime() < rightData.toDateTime();
     } else {
         QRegExp *emailPattern = new QRegExp("([\\w\\.]*@[\\w\\.]*)");

         QString leftString = leftData.toString();
         if(left.column() == 1 && emailPattern->indexIn(leftString) != -1)
             leftString = emailPattern->cap(1);

         QString rightString = rightData.toString();
         if(right.column() == 1 && emailPattern->indexIn(rightString) != -1)
             rightString = emailPattern->cap(1);

         return QString::localeAwareCompare(leftString, rightString) < 0;
     }
 }

(This code snippet comes from the Custom Sort/Filter Model example.)

An alternative approach to sorting is to disable sorting on the view and to impose a certain order to the user. This is done by explicitly calling sort() with the desired column and order as arguments on the QSortFilterProxyModel (or on the original model if it implements sort()). For example:

         proxyModel->sort(2, Qt::AscendingOrder);

QSortFilterProxyModel can be sorted by column -1, in which case it returns to the sort order of the underlying source model.

         proxyModel->setFilterRegExp(QRegExp(".png", Qt::CaseInsensitive,
                                             QRegExp::FixedString));
         proxyModel->setFilterKeyColumn(1);

 bool MySortFilterProxyModel::filterAcceptsRow(int sourceRow,
         const QModelIndex &sourceParent) const
 {
     QModelIndex index0 = sourceModel()->index(sourceRow, 0, sourceParent);
     QModelIndex index1 = sourceModel()->index(sourceRow, 1, sourceParent);
     QModelIndex index2 = sourceModel()->index(sourceRow, 2, sourceParent);

     return (sourceModel()->data(index0).toString().contains(filterRegExp())
             || sourceModel()->data(index1).toString().contains(filterRegExp()))
            && dateInRange(sourceModel()->data(index2).toDate());
 }