- Qt 5.15
- Qt Core
- C++ Classes
- QIdentityProxyModel
- Qt 5.15.18 Reference Documentation

# QIdentityProxyModel Class

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

Header: | #include <QIdentityProxyModel>
qmake: | QT += core
Since: | Qt 4.8
Inherits: | QAbstractProxyModel

This class was introduced in Qt 4.8.

- List of all members, including inherited members

## Public Functions

| QIdentityProxyModel(QObject *parent = nullptr)
virtual | ~QIdentityProxyModel()

## 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

## 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 QDateTime dateTime = sourceModel()->data(SourceClass::DateRole).toDateTime();

         return dateTime.toString(m_formatString);
       }

     private:
       QString m_formatString;
     };

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

## Member Function Documentation

### QIdentityProxyModel::QIdentityProxyModel(QObject *parent = nullptr)

Constructs an identity model with the given parent.

### `[virtual]` 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).

### `[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).

This function was introduced in Qt 5.15.

### `[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).

This function was introduced in Qt 5.15.

### `[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.

### `[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.