QModelIndex Class Reference

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

  1. #include <QModelIndex>

Detailed Description

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

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.

Public Functions

Toggle details QModelIndex

QModelIndexQModelIndex () ()

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.

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Toggle details QModelIndex

QModelIndexQModelIndex ( const QModelIndex &other ) ( const QModelIndex &other )

Creates a new model index that is a copy of the other model index.

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Toggle details QModelIndex

~QModelIndex~QModelIndex () ()

Destroys the model index.

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Toggle details QModelIndex QModelIndex

childchild ( int row , int column ) ( int row , int column )const

Returns the child of the model index that is stored in the given row and column.

Note: This function does not work for an invalid model index which is often used as the root index.

See also parent() and sibling().

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Toggle details int QModelIndex

columncolumn () ()const

Returns the column this model index refers to.

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Toggle details QVariant QModelIndex

datadata ( int role=Qt::DisplayRole ) ( int role=Qt::DisplayRole )const

Returns the data for the given role for the item referred to by the index.

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Toggle details Qt::ItemFlags QModelIndex

flagsflags () ()const

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

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Toggle details qint64 QModelIndex

internalIdinternalId () ()const

Returns a qint64 used by the model to associate the index with the internal data structure.

See also QAbstractItemModel::createIndex().

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Toggle details void * QModelIndex

internalPointerinternalPointer () ()const

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

See also QAbstractItemModel::createIndex().

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Toggle details bool QModelIndex

isValidisValid () ()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().

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Toggle details const QAbstractItemModel * QModelIndex

modelmodel () ()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.

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Toggle details QModelIndex QModelIndex

parentparent () ()const

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

See also child(), sibling(), and model().

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Toggle details int QModelIndex

rowrow () ()const

Returns the row this model index refers to.

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Toggle details QModelIndex QModelIndex

siblingsibling ( int row , int column ) ( 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() and child().

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Toggle details bool QModelIndex

operator!=operator!= ( const QModelIndex &other ) ( const QModelIndex &other )const

Returns true if this model index does not refer to the same location as the other model index; otherwise returns false.

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Toggle details bool QModelIndex

operator<operator< ( const QModelIndex &other ) ( const QModelIndex &other )const

Returns true if this model index is smaller than the other model index; otherwise returns false.

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Toggle details bool QModelIndex

operator==operator== ( const QModelIndex &other ) ( const QModelIndex &other )const

Returns true if this model index refers to the same location as the other model index; otherwise returns false.

All values in the model index are used when comparing with another model index.

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