- Qt 6.9
- Qt Core
- C++ Classes
- QIdentityProxyModel
- Qt 6.9.3 Reference Documentation

# QIdentityProxyModel Class

The QIdentityProxyModel class proxies its source model unmodified. More...

Header: | `#include <QIdentityProxyModel>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`
Inherits: | QAbstractProxyModel

- List of all members, including inherited members

## Public Functions

| QIdentityProxyModel(QObject *parent = nullptr)
virtual | ~QIdentityProxyModel()
`(since 6.8)` bool | handleSourceDataChanges() const
`(since 6.8)` bool | handleSourceLayoutChanges() const

## Reimplemented Public Functions

virtual int | columnCount(const QModelIndex &parent = QModelIndex()) const override
virtual bool | dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent) override
virtual QVariant | headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const override
virtual QModelIndex | index(int row, int column, const QModelIndex &parent = QModelIndex()) const override
virtual bool | insertColumns(int column, int count, const QModelIndex &parent = QModelIndex()) override
virtual bool | insertRows(int row, int count, const QModelIndex &parent = QModelIndex()) override
virtual QModelIndex | mapFromSource(const QModelIndex &sourceIndex) const override
virtual QItemSelection | mapSelectionFromSource(const QItemSelection &selection) const override
virtual QItemSelection | mapSelectionToSource(const QItemSelection &selection) const override
virtual QModelIndex | mapToSource(const QModelIndex &proxyIndex) const override
virtual QModelIndexList | match(const QModelIndex &start, int role, const QVariant &value, int hits = 1, Qt::MatchFlags flags = Qt::MatchFlags(Qt::MatchStartsWith|Qt::MatchWrap)) const override
virtual bool | moveColumns(const QModelIndex &sourceParent, int sourceColumn, int count, const QModelIndex &destinationParent, int destinationChild) override
virtual bool | moveRows(const QModelIndex &sourceParent, int sourceRow, int count, const QModelIndex &destinationParent, int destinationChild) override
virtual QModelIndex | parent(const QModelIndex &child) const override
virtual bool | removeColumns(int column, int count, const QModelIndex &parent = QModelIndex()) override
virtual bool | removeRows(int row, int count, const QModelIndex &parent = QModelIndex()) override
virtual int | rowCount(const QModelIndex &parent = QModelIndex()) const override
virtual void | setSourceModel(QAbstractItemModel *newSourceModel) override
virtual QModelIndex | sibling(int row, int column, const QModelIndex &idx) const override

## Protected Functions

`(since 6.8)` void | setHandleSourceDataChanges(bool b)
`(since 6.8)` void | setHandleSourceLayoutChanges(bool b)

## Detailed Description

QIdentityProxyModel can be used to forward the structure of a source model exactly, with no sorting, filtering or other transformation. This is similar in concept to an identity matrix where A.I = A.

Because it does no sorting or filtering, this class is most suitable to proxy models which transform the data() of the source model. For example, a proxy model could be created to define the font used, or the background colour, or the tooltip etc. This removes the need to implement all data handling in the same class that creates the structure of the model, and can also be used to create re-usable components.

This also provides a way to change the data in the case where a source model is supplied by a third party which cannot be modified.

     class DateFormatProxyModel : public QIdentityProxyModel
     {
       // ...

       void setDateFormatString(const QString &formatString)
       {
         m_formatString = formatString;
       }

       QVariant data(const QModelIndex &index, int role) const override
       {
         if (role != Qt::DisplayRole)
           return QIdentityProxyModel::data(index, role);

         const QModelIndex sourceIndex = mapToSource(index);
         const QDateTime dateTime = sourceModel()->data(sourceIndex, SourceClass::DateRole).toDateTime();
         return dateTime.toString(m_formatString);
       }

       QMap<int, QVariant> itemData(const QModelIndex &proxyIndex) const override
       {
           QMap<int, QVariant> map = QIdentityProxyModel::itemData(proxyIndex);
           map[Qt::DisplayRole] = data(proxyIndex);
           return map;
       }

     private:
       QString m_formatString;
     };

See also QAbstractProxyModel, Model/View Programming, and QAbstractItemModel.

## Member Function Documentation

### `[explicit]` QIdentityProxyModel::QIdentityProxyModel(QObject *parent = nullptr)

Constructs an identity model with the given parent.

### `[virtual noexcept]` QIdentityProxyModel::~QIdentityProxyModel()

Destroys this identity model.

### `[override virtual]` int QIdentityProxyModel::columnCount(const QModelIndex &parent = QModelIndex()) const

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

### `[override virtual]` bool QIdentityProxyModel::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)

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

### `[since 6.8]` bool QIdentityProxyModel::handleSourceDataChanges() const

Returns `true` if this proxy model handles the source model data changes, otherwise returns `false`.

This function was introduced in Qt 6.8.

See also setHandleSourceDataChanges().

### `[since 6.8]` bool QIdentityProxyModel::handleSourceLayoutChanges() const

Returns `true` if this proxy model handles the source model layout changes, otherwise returns `false`.

This function was introduced in Qt 6.8.

See also setHandleSourceLayoutChanges().

### `[override virtual]` QVariant QIdentityProxyModel::headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const

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

### `[override virtual]` QModelIndex QIdentityProxyModel::index(int row, int column, const QModelIndex &parent = QModelIndex()) const

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

### `[override virtual]` bool QIdentityProxyModel::insertColumns(int column, int count, const QModelIndex &parent = QModelIndex())

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

### `[override virtual]` bool QIdentityProxyModel::insertRows(int row, int count, const QModelIndex &parent = QModelIndex())

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

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

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

### `[override virtual]` QItemSelection QIdentityProxyModel::mapSelectionFromSource(const QItemSelection &selection) const

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

### `[override virtual]` QItemSelection QIdentityProxyModel::mapSelectionToSource(const QItemSelection &selection) const

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

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

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

### `[override virtual]` QModelIndexList QIdentityProxyModel::match(const QModelIndex &start, int role, const QVariant &value, int hits = 1, Qt::MatchFlags flags = Qt::MatchFlags(Qt::MatchStartsWith|Qt::MatchWrap)) const

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

### `[override virtual]` bool QIdentityProxyModel::moveColumns(const QModelIndex &sourceParent, int sourceColumn, int count, const QModelIndex &destinationParent, int destinationChild)

Reimplements: QAbstractItemModel::moveColumns(const QModelIndex &sourceParent, int sourceColumn, int count, const QModelIndex &destinationParent, int destinationChild).

### `[override virtual]` bool QIdentityProxyModel::moveRows(const QModelIndex &sourceParent, int sourceRow, int count, const QModelIndex &destinationParent, int destinationChild)

Reimplements: QAbstractItemModel::moveRows(const QModelIndex &sourceParent, int sourceRow, int count, const QModelIndex &destinationParent, int destinationChild).

### `[override virtual]` QModelIndex QIdentityProxyModel::parent(const QModelIndex &child) const

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

### `[override virtual]` bool QIdentityProxyModel::removeColumns(int column, int count, const QModelIndex &parent = QModelIndex())

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

### `[override virtual]` bool QIdentityProxyModel::removeRows(int row, int count, const QModelIndex &parent = QModelIndex())

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

### `[override virtual]` int QIdentityProxyModel::rowCount(const QModelIndex &parent = QModelIndex()) const

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

### `[protected, since 6.8]` void QIdentityProxyModel::setHandleSourceDataChanges(bool b)

If b is `true`, this proxy model will handle the source model data changes (by connecting to `QAbstractItemModel::dataChanged` signal).

The default is for this proxy model to handle the source model data changes.

In sub-classes of QIdentityProxyModel, it may be useful to set this to `false` if you need to specially handle the source model data changes.

Note: Calling this method will only have an effect after calling setSourceModel().

This function was introduced in Qt 6.8.

See also handleSourceDataChanges().

### `[protected, since 6.8]` void QIdentityProxyModel::setHandleSourceLayoutChanges(bool b)

If b is `true`, this proxy model will handle the source model layout changes (by connecting to `QAbstractItemModel::layoutAboutToBeChanged` and `QAbstractItemModel::layoutChanged` signals).

The default is for this proxy model to handle the source model layout changes.

In sub-classes of QIdentityProxyModel, it may be useful to set this to `false` if you need to specially handle the source model layout changes.

Note: Calling this method will only have an effect after calling setSourceModel().

This function was introduced in Qt 6.8.

See also handleSourceLayoutChanges().

### `[override virtual]` void QIdentityProxyModel::setSourceModel(QAbstractItemModel *newSourceModel)

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

### `[override virtual]` QModelIndex QIdentityProxyModel::sibling(int row, int column, const QModelIndex &idx) const

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