- Qt 6.8
- Qt Core
- C++ Classes
- QModelIndex
- Qt 6.8.3 Reference Documentation

# QModelIndex Class

The QModelIndex class is used to locate data in a data model. More...

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

- List of all members, including inherited members

This class is strongly comparable.

## Public Functions

| QModelIndex()
int | column() const
const void * | constInternalPointer() const
QVariant | data(int role = Qt::DisplayRole) const
Qt::ItemFlags | flags() const
quintptr | internalId() const
void * | internalPointer() const
bool | isValid() const
const QAbstractItemModel * | model() const
`(since 6.0)` void | multiData(QModelRoleDataSpan roleDataSpan) const
QModelIndex | parent() const
int | row() const
QModelIndex | sibling(int row, int column) const
QModelIndex | siblingAtColumn(int column) const
QModelIndex | siblingAtRow(int row) const

## Related Non-Members

| QModelIndexList
bool | operator!=(const QModelIndex &lhs, const QModelIndex &rhs)
bool | operator<(const QModelIndex &lhs, const QModelIndex &rhs)
bool | operator==(const QModelIndex &lhs, const QModelIndex &rhs)

## Detailed Description

This class is used as an index into item models derived from QAbstractItemModel. The index is used by item views, delegates, and selection models to locate an item in the model.

New QModelIndex objects are created by the model using the QAbstractItemModel::createIndex() function. An invalid model index can be constructed with the QModelIndex constructor. Invalid indexes are often used as parent indexes when referring to top-level items in a model.

Model indexes refer to items in models, and contain all the information required to specify their locations in those models. Each index is located in a given row and column, and may have a parent index; use row(), column(), and parent() to obtain this information. Each top-level item in a model is represented by a model index that does not have a parent index - in this case, parent() will return an invalid model index, equivalent to an index constructed with the zero argument form of the QModelIndex() constructor.

To obtain a model index that refers to an existing item in a model, call QAbstractItemModel::index() with the required row and column values, and the model index of the parent. When referring to top-level items in a model, supply QModelIndex() as the parent index.

The model() function returns the model that the index references as a QAbstractItemModel. The child() function is used to examine items held under the index in the model. The sibling() function allows you to traverse items in the model on the same level as the index.

Note: Model indexes should be used immediately and then discarded. You should not rely on indexes to remain valid after calling model functions that change the structure of the model or delete items. If you need to keep a model index over time use a QPersistentModelIndex.

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

## Member Function Documentation

### `[constexpr noexcept]` QModelIndex::QModelIndex()

Creates a new empty model index. This type of model index is used to indicate that the position in the model is invalid.

See also isValid() and QAbstractItemModel.

### `[constexpr noexcept]` int QModelIndex::column() const

Returns the column this model index refers to.

### `[noexcept]` const void *QModelIndex::constInternalPointer() const

Returns a `const void` `*` pointer used by the model to associate the index with the internal data structure.

See also QAbstractItemModel::createIndex().

### QVariant QModelIndex::data(int role = Qt::DisplayRole) const

Returns the data for the given role for the item referred to by the index, or a default-constructed QVariant if this model index is invalid.

### Qt::ItemFlags QModelIndex::flags() const

Returns the flags for the item referred to by the index.

### `[constexpr noexcept]` quintptr QModelIndex::internalId() const

Returns a `quintptr` used by the model to associate the index with the internal data structure.

See also QAbstractItemModel::createIndex().

### `[noexcept]` void *QModelIndex::internalPointer() const

Returns a `void` `*` pointer used by the model to associate the index with the internal data structure.

See also QAbstractItemModel::createIndex().

### `[constexpr noexcept]` bool QModelIndex::isValid() const

Returns `true` if this model index is valid; otherwise returns `false`.

A valid index belongs to a model, and has non-negative row and column numbers.

See also model(), row(), and column().

### `[constexpr noexcept]` const QAbstractItemModel *QModelIndex::model() const

Returns a pointer to the model containing the item that this index refers to.

A const pointer to the model is returned because calls to non-const functions of the model might invalidate the model index and possibly crash your application.

### `[since 6.0]` void QModelIndex::multiData(QModelRoleDataSpan roleDataSpan) const

Populates the given roleDataSpan for the item referred to by the index.

This function was introduced in Qt 6.0.

### QModelIndex QModelIndex::parent() const

Returns the parent of the model index, or QModelIndex() if it has no parent.

See also sibling() and model().

### `[constexpr noexcept]` int QModelIndex::row() const

Returns the row this model index refers to.

### QModelIndex QModelIndex::sibling(int row, int column) const

Returns the sibling at row and column. If there is no sibling at this position, an invalid QModelIndex is returned.

See also parent(), siblingAtColumn(), and siblingAtRow().

### QModelIndex QModelIndex::siblingAtColumn(int column) const

Returns the sibling at column for the current row. If there is no sibling at this position, an invalid QModelIndex is returned.

See also sibling() and siblingAtRow().

### QModelIndex QModelIndex::siblingAtRow(int row) const

Returns the sibling at row for the current column. If there is no sibling at this position, an invalid QModelIndex is returned.

See also sibling() and siblingAtColumn().

## Related Non-Members

### QModelIndexList

Synonym for QList<QModelIndex>.

### `[constexpr noexcept]` bool operator!=(const QModelIndex &lhs, const QModelIndex &rhs)

Returns `true` if lhs model index does not refer to the same location as the rhs model index; otherwise returns `false`.

### `[constexpr noexcept]` bool operator<(const QModelIndex &lhs, const QModelIndex &rhs)

Returns `true` if lhs model index is smaller than the rhs model index; otherwise returns `false`.

The less than calculation is not directly useful to developers - the way that indexes with different parents compare is not defined. This operator only exists so that the class can be used with QMap.

### `[constexpr noexcept]` bool operator==(const QModelIndex &lhs, const QModelIndex &rhs)

Returns `true` if lhs model index refers to the same location as the rhs model index; otherwise returns `false`.

The internal data pointer, row, column, and model values are used when comparing with another model index.