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# QSortFilterProxyModel Class Reference
[QtGui module]

The QSortFilterProxyModel class provides support for sorting and filtering data passed between another model and a view. More...

     #include <QSortFilterProxyModel>

Inherits QAbstractProxyModel.

This class was introduced in Qt 4.1.

- List of all members, including inherited members

### Properties

dynamicSortFilter : bool filterCaseSensitivity : Qt::CaseSensitivity filterKeyColumn : int filterRegExp : QRegExp | filterRole : int sortCaseSensitivity : Qt::CaseSensitivity sortRole : int

- 1 property inherited from QObject

### Public Functions

- QSortFilterProxyModel ( QObject * parent = 0 )
- ~QSortFilterProxyModel ()
- bool dynamicSortFilter () const
- Qt::CaseSensitivity filterCaseSensitivity () const
- int filterKeyColumn () const
- QRegExp filterRegExp () const
- int filterRole () const
- virtual QModelIndex mapFromSource ( const QModelIndex & sourceIndex ) const
- virtual QModelIndex mapToSource ( const QModelIndex & proxyIndex ) const
- void setDynamicSortFilter ( bool enable )
- void setFilterCaseSensitivity ( Qt::CaseSensitivity cs )
- void setFilterKeyColumn ( int column )
- void setFilterRegExp ( const QRegExp & regExp )
- void setFilterRole ( int role )
- void setSortCaseSensitivity ( Qt::CaseSensitivity cs )
- void setSortRole ( int role )
- Qt::CaseSensitivity sortCaseSensitivity () const
- int sortRole () const

- 6 public functions inherited from QAbstractProxyModel
- 34 public functions inherited from QAbstractItemModel
- 29 public functions inherited from QObject

### Public Slots

- void clear ()
- void setFilterFixedString ( const QString & pattern )
- void setFilterRegExp ( const QString & pattern )
- void setFilterWildcard ( const QString & pattern )

- 2 public slots inherited from QAbstractItemModel
- 1 public slot inherited from QObject

### Protected Functions

- virtual bool filterAcceptsColumn ( int source_column, const QModelIndex & source_parent ) const
- virtual bool filterAcceptsRow ( int source_row, const QModelIndex & source_parent ) const
- void filterChanged ()
- virtual bool lessThan ( const QModelIndex & left, const QModelIndex & right ) const

- 14 protected functions inherited from QAbstractItemModel
- 7 protected functions inherited from QObject

### Additional Inherited Members

- 14 signals inherited from QAbstractItemModel
- 1 signal inherited from QObject
- 5 static public members inherited from QObject

## Detailed Description

The QSortFilterProxyModel class provides support for sorting and filtering data passed between another model and a view.

QSortFilterProxyModel can be used for sorting items, filtering out items, or both. The model transforms the structure of a source model by mapping the model indexes it supplies to new indexes, corresponding to different locations, for views to use. This approach allows a given source model to be restructured as far as views are concerned without requiring any transformations on the underlying data, and without duplicating the data in memory.

Let's assume that we want to sort and filter the items provided by a custom model. The code to set up the model and the view, without sorting and filtering, would look like this:

             QTreeView *treeView = new QTreeView;
             MyItemModel *model = new MyItemModel(this);

             treeView->setModel(model);

To add sorting and filtering support to `MyItemModel`, we need to create a QSortFilterProxyModel, call setSourceModel() with the `MyItemModel` as argument, and install the QSortFilterProxyModel on the view:

             QTreeView *treeView = new QTreeView;
             MyItemModel *sourceModel = new MyItemModel(this);
             QSortFilterProxyModel *proxyModel = new QSortFilterProxyModel(this);

             proxyModel->setSourceModel(sourceModel);
             treeView->setModel(proxyModel);

At this point, neither sorting nor filtering is enabled; the original data is displayed in the view. Any changes made through the QSortFilterProxyModel are applied to the original model.

The QSortFilterProxyModel acts as a wrapper for the original model. If you need to convert source QModelIndexes to sorted/filtered model indexes or vice versa, use mapToSource(), mapFromSource(), mapSelectionToSource(), and mapSelectionFromSource().

In Qt 4.1, sorting and filtering isn't dynamically reapplied whenever the data of the original model changes, as an optimization. Qt 4.2 is expected to offer a mechanism to enable dynamic sorting and filtering.

The Basic Sort/Filter Model and Custom Sort/Filter Model examples illustrate how to use QSortFilterProxyModel to perform basic sorting and filtering and how to subclass it to implement custom behavior.

### 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 you 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 {
             return QString::localeAwareCompare(leftData.toString(),
                                                rightData.toString()) < 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);

### Filtering

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

             proxyModel->setFilterRegExp(QRegExp(".png", Qt::CaseInsensitive,
                                                 QRegExp::FixedString));
             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 regexp, wildcard pattern, or fixed string in a QLineEdit and to connect the textChanged() signal to setFilterRegExp(), setFilterWildcard(), or setFilterFixedString() to reapply the filter.

Custom filtering behavior can be achieved by reimplementing the filterAcceptsRow() and filterAcceptsColumn() functions. For 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(filterRegExp())
                 || sourceModel()->data(index1).toString().contains(filterRegExp()))
                && dateInRange(sourceModel()->data(index2).toDate());
     }

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

### Subclassing

Note: Some general guidelines for subclassing models are available in the Model Subclassing Reference.

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, and Custom Sort/Filter Model Example.

## Property Documentation

### dynamicSortFilter : bool

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

The default value is false.

This property was introduced in Qt 4.2.

Access functions:

- bool dynamicSortFilter () const
- void setDynamicSortFilter ( bool enable )

### filterCaseSensitivity : Qt::CaseSensitivity

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

By default, the filter is case sensistive.

Access functions:

- Qt::CaseSensitivity filterCaseSensitivity () const
- void setFilterCaseSensitivity ( Qt::CaseSensitivity cs )

See also filterRegExp and sortCaseSensitivity.

### filterKeyColumn : int

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.

Access functions:

- int filterKeyColumn () const
- void setFilterKeyColumn ( int column )

### filterRegExp : QRegExp

This property holds the QRegExp used to filter the contents of the source model.

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

Access functions:

- QRegExp filterRegExp () const
- void setFilterRegExp ( const QRegExp & regExp )
- void setFilterRegExp ( const QString & pattern )

See also filterCaseSensitivity, setFilterWildcard(), and setFilterFixedString().

### filterRole : int

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.

This property was introduced in Qt 4.2.

Access functions:

- int filterRole () const
- void setFilterRole ( int role )

See also filterAcceptsRow().

### sortCaseSensitivity : Qt::CaseSensitivity

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

By default, sorting is case sensistive.

This property was introduced in Qt 4.2.

Access functions:

- Qt::CaseSensitivity sortCaseSensitivity () const
- void setSortCaseSensitivity ( Qt::CaseSensitivity cs )

See also filterCaseSensitivity and lessThan().

### sortRole : int

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.

This property was introduced in Qt 4.2.

Access functions:

- int sortRole () const
- void setSortRole ( int role )

See also lessThan().

## Member Function Documentation

### QSortFilterProxyModel::QSortFilterProxyModel ( QObject * parent = 0 )

Constructs a sorting filter model with the given parent.

### QSortFilterProxyModel::~QSortFilterProxyModel ()

Destroys this sorting filter model.

### void QSortFilterProxyModel::clear () `[slot]`

Clears this sorting filter model, removing all mapping.

See also filterChanged().

### bool QSortFilterProxyModel::filterAcceptsColumn ( int source_column, const QModelIndex & source_parent ) const `[virtual protected]`

Returns true if the value in the item in the column indicated by the given source_column and source_parent should be included in the model.

The default implementation returns true.

See also filterAcceptsRow().

### bool QSortFilterProxyModel::filterAcceptsRow ( int source_row, const QModelIndex & source_parent ) const `[virtual protected]`

Returns true if the value in the item in the row indicated by the given source_row and source_parent should be included in the model.

By default, the Qt::DisplayRole is used to determine if the row should be accepted or not. This can be changed by setting the filterRole property.

See also filterRole, filterKeyColumn, filterRegExp, and filterAcceptsColumn().

### void QSortFilterProxyModel::filterChanged () `[protected]`

Updates the mapping to reflect a change in the filter.

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

This function was introduced in Qt 4.2.

See also clear().

### bool QSortFilterProxyModel::lessThan ( const QModelIndex & left, const QModelIndex & right ) const `[virtual protected]`

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

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

- QVariant::Int
- QVariant::UInt
- QVariant::LongLong
- QVariant::ULongLong
- QVariant::Double
- QVariant::Char
- QVariant::Date
- QVariant::Time
- QVariant::DateTime
- QVariant::String

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.

See also sortRole, sortCaseSensitivity, and dynamicSortFilter.

### QModelIndex QSortFilterProxyModel::mapFromSource ( const QModelIndex & sourceIndex ) const `[virtual]`

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

Reimplemented from QAbstractProxyModel.

See also mapToSource().

### QModelIndex QSortFilterProxyModel::mapToSource ( const QModelIndex & proxyIndex ) const `[virtual]`

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

Reimplemented from QAbstractProxyModel.

See also mapFromSource().

### void QSortFilterProxyModel::setFilterFixedString ( const QString & pattern ) `[slot]`

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

See also setFilterCaseSensitivity(), setFilterRegExp(), setFilterWildcard(), and filterRegExp().

### void QSortFilterProxyModel::setFilterWildcard ( const QString & pattern ) `[slot]`

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

See also setFilterCaseSensitivity(), setFilterRegExp(), setFilterFixedString(), and filterRegExp().