QSortFilterProxyModel Class

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.userType() == QMetaType::QDateTime) {
        return leftData.toDateTime() < rightData.toDateTime();
    } else {
        static const QRegularExpression emailPattern("[\\w\\.]*@[\\w\\.]*");

        QString leftString = leftData.toString();
        if (left.column() == 1) {
            const QRegularExpressionMatch match = emailPattern.match(leftString);
            if (match.hasMatch())
                leftString = match.captured(0);
        }
        QString rightString = rightData.toString();
        if (right.column() == 1) {
            const QRegularExpressionMatch match = emailPattern.match(rightString);
            if (match.hasMatch())
                rightString = match.captured(0);
        }

        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.

In addition to sorting, QSortFilterProxyModel can be used to hide items that do not match a certain filter. The filter is specified using a QRegularExpression object and is applied to the filterRole() (Qt::DisplayRole by default) of each item, for a given column. The QRegularExpression object can be used to match a regular expression, a wildcard pattern, or a fixed string. For example:

        proxyModel->setFilterRegularExpression(QRegularExpression("\.png", QRegularExpression::CaseInsensitiveOption));
        proxyModel->setFilterKeyColumn(1);

For hierarchical models, the filter is applied recursively to all children. If a parent item doesn't match the filter, none of its children will be shown.

A common use case is to let the user specify the filter regular expression, wildcard pattern, or fixed string in a QLineEdit and to connect the textChanged() signal to setFilterRegularExpression(), setFilterWildcard(), or setFilterFixedString() to reapply the filter.

Custom filtering behavior can be achieved by reimplementing the filterAcceptsRow() and filterAcceptsColumn() functions. For example (from the Custom Sort/Filter Model example), the following implementation ignores the filterKeyColumn property and performs filtering on columns 0, 1, and 2:

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

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

If you are working with large amounts of filtering and have to invoke invalidateFilter() repeatedly, using beginResetModel() / endResetModel() may be more efficient, depending on the implementation of your model. However, beginResetModel() / endResetModel() returns the proxy model to its original state, losing selection information, and will cause the proxy model to be repopulated.

Since QAbstractProxyModel and its subclasses are derived from QAbstractItemModel, much of the same advice about subclassing normal models also applies to proxy models. In addition, it is worth noting that many of the default implementations of functions in this class are written so that they call the equivalent functions in the relevant source model. This simple proxying mechanism may need to be overridden for source models with more complex behavior; for example, if the source model provides a custom hasChildren() implementation, you should also provide one in the proxy model.

See also QAbstractProxyModel, QAbstractItemModel, Model/View Programming, Basic Sort/Filter Model Example, Custom Sort/Filter Model Example, QIdentityProxyModel

This property supports QProperty bindings.

if true the proxy model will not filter out children of accepted rows, even if they themselves would be filtered out otherwise.

The default value is false.

This property was introduced in Qt 6.0.

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This property supports QProperty bindings.

This property holds whether the proxy model is dynamically sorted and filtered whenever the contents of the source model change

Note that you should not update the source model through the proxy model when dynamicSortFilter is true. For instance, if you set the proxy model on a QComboBox, then using functions that update the model, e.g., addItem(), will not work as expected. An alternative is to set dynamicSortFilter to false and call sort() after adding items to the QComboBox.

The default value is true.

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This property supports QProperty bindings.

This property holds the case sensitivity of the QRegularExpression pattern used to filter the contents of the source model.

By default, the filter is case sensitive.

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This property supports QProperty bindings.

This property holds the column where the key used to filter the contents of the source model is read from.

The default value is 0. If the value is -1, the keys will be read from all columns.

This property supports QProperty bindings.

This property holds the QRegularExpression used to filter the contents of the source model

Setting this property through the QRegularExpression overload overwrites the current filterCaseSensitivity. By default, the QRegularExpression is an empty string matching all contents.

If no QRegularExpression or an empty string is set, everything in the source model will be accepted.

This property was introduced in Qt 5.12.

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This property supports QProperty bindings.

This property holds the item role that is used to query the source model's data when filtering items.

The default value is Qt::DisplayRole.

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This property supports QProperty bindings.

This property holds the local aware setting used for comparing strings when sorting

By default, sorting is not local aware.

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This property supports QProperty bindings.

This property holds whether the filter to be applied recursively on children, and for any matching child, its parents will be visible as well.

The default value is false.

This property was introduced in Qt 5.10.

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This property supports QProperty bindings.

This property holds the case sensitivity setting used for comparing strings when sorting

By default, sorting is case sensitive.

See Also▲

This property supports QProperty bindings.

This property holds the item role that is used to query the source model's data when sorting items.

The default value is Qt::DisplayRole.

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Constructs a sorting filter model with the given parent.

Destroys this sorting filter model.

This signals is emitted when the value of the autoAcceptChildRows property is changed.

This function was introduced in Qt 6.0.

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Reimplements: QAbstractProxyModel::buddy(const QModelIndex &index) const.

Reimplements: QAbstractProxyModel::canFetchMore(const QModelIndex &parent) const.

Reimplements: QAbstractItemModel::columnCount(const QModelIndex &parent) const.

Reimplements: QAbstractProxyModel::data(const QModelIndex &proxyIndex, int role) const.

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Reimplements: QAbstractProxyModel::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent).

Reimplements: QAbstractProxyModel::fetchMore(const QModelIndex &parent).

Returns true if the item in the column indicated by the given source_column and source_parent should be included in the model; otherwise returns false.

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Returns true if the item in the row indicated by the given source_row and source_parent should be included in the model; otherwise returns false.

The default implementation returns true if the value held by the relevant item matches the filter string, wildcard string or regular expression.

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This signal is emitted when the case sensitivity of the filter changes to filterCaseSensitivity.

This function was introduced in Qt 5.15.

This signal is emitted when the filter role changes to filterRole.

This function was introduced in Qt 5.15.

Reimplements: QAbstractProxyModel::flags(const QModelIndex &index) const.

Reimplements: QAbstractProxyModel::hasChildren(const QModelIndex &parent) const.

Reimplements: QAbstractProxyModel::headerData(int section, Qt::Orientation orientation, int role) const.

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Reimplements: QAbstractItemModel::index(int row, int column, const QModelIndex &parent) const.

Reimplements: QAbstractItemModel::insertColumns(int column, int count, const QModelIndex &parent).

Reimplements: QAbstractItemModel::insertRows(int row, int count, const QModelIndex &parent).

Invalidates the current sorting and filtering.

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Invalidates the current filtering for the columns.

This function should be called if you are implementing custom filtering (by filterAcceptsColumn()), and your filter parameters have changed. This differs from invalidateFilter() in that it will not invoke filterAcceptsRow(), but only filterAcceptsColumn(). You can use this instead of invalidateFilter() if you want to hide or show a column where the rows don't change.

This function was introduced in Qt 6.0.

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Invalidates the current filtering.

This function should be called if you are implementing custom filtering (e.g. filterAcceptsRow()), and your filter parameters have changed.

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Invalidates the current filtering for the rows.

This function should be called if you are implementing custom filtering (by filterAcceptsRow()), and your filter parameters have changed. This differs from invalidateFilter() in that it will not invoke filterAcceptsColumn(), but only filterAcceptsRow(). You can use this instead of invalidateFilter() if you want to hide or show a row where the columns don't change.

This function was introduced in Qt 6.0.

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Returns true if the value of the item referred to by the given index source_left is less than the value of the item referred to by the given index source_right, otherwise returns false.

This function is used as the < operator when sorting, and handles the following QVariant types:

• QMetaType::Int

• QMetaType::UInt

• QMetaType::LongLong

• QMetaType::ULongLong

• QMetaType::Float

• QMetaType::Double

• QMetaType::QChar

• QMetaType::QDate

• QMetaType::QTime

• QMetaType::QDateTime

• QMetaType::QString

Any other type will be converted to a QString using QVariant::toString().

Comparison of QStrings is case sensitive by default; this can be changed using the sortCaseSensitivity property.

By default, the Qt::DisplayRole associated with the QModelIndexes is used for comparisons. This can be changed by setting the sortRole property.

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Reimplements: QAbstractProxyModel::mapFromSource(const QModelIndex &sourceIndex) const.

Returns the model index in the QSortFilterProxyModel given the sourceIndex from the source model.

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Reimplements: QAbstractProxyModel::mapSelectionFromSource(const QItemSelection &sourceSelection) const.

Reimplements: QAbstractProxyModel::mapSelectionToSource(const QItemSelection &proxySelection) const.

Reimplements: QAbstractProxyModel::mapToSource(const QModelIndex &proxyIndex) const.

Returns the source model index corresponding to the given proxyIndex from the sorting filter model.

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Reimplements: QAbstractItemModel::match(const QModelIndex &start, int role, const QVariant &value, int hits, Qt::MatchFlags flags) const.

Reimplements: QAbstractProxyModel::mimeData(const QModelIndexList &indexes) const.

Reimplements: QAbstractProxyModel::mimeTypes() const.

Reimplements: QAbstractItemModel::parent(const QModelIndex &index) const.

This signal is emitted when the recursive filter setting is changed to recursiveFilteringEnabled.

This function was introduced in Qt 5.15.

Reimplements: QAbstractItemModel::removeColumns(int column, int count, const QModelIndex &parent).

Reimplements: QAbstractItemModel::removeRows(int row, int count, const QModelIndex &parent).

Reimplements: QAbstractItemModel::rowCount(const QModelIndex &parent) const.

Reimplements: QAbstractProxyModel::setData(const QModelIndex &index, const QVariant &value, int role).

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Sets the fixed string used to filter the contents of the source model to the given pattern.

This method will reset the regular expression options but respect case sensitivity.

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Sets the regular expression used to filter the contents of the source model to pattern.

This method should be preferred for new code as it will use QRegularExpression internally.

This method will reset the regular expression options but respect case sensitivity.

This function was introduced in Qt 5.12.

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Sets the wildcard expression used to filter the contents of the source model to the given pattern.

This method will reset the regular expression options but respect case sensitivity.

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Reimplements: QAbstractProxyModel::setHeaderData(int section, Qt::Orientation orientation, const QVariant &value, int role).

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Reimplements: QAbstractProxyModel::setSourceModel(QAbstractItemModel *sourceModel).

Reimplements: QAbstractProxyModel::sibling(int row, int column, const QModelIndex &idx) const.

Reimplements: QAbstractProxyModel::sort(int column, Qt::SortOrder order).

This signal is emitted when the case sensitivity for sorting changes to sortCaseSensitivity.

This function was introduced in Qt 5.15.

Returns the column currently used for sorting

This returns the most recently used sort column. The default value is -1, which means that this proxy model does not sort.

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This signal is emitted when the locale aware setting changes to sortLocaleAware.

This function was introduced in Qt 5.15.

Returns the order currently used for sorting

This returns the most recently used sort order. The default value is Qt::AscendingOrder.

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This signal is emitted when the sort role changes to sortRole.

This function was introduced in Qt 5.15.

Reimplements: QAbstractProxyModel::span(const QModelIndex &index) const.

Reimplements: QAbstractProxyModel::supportedDropActions() const.