- Qt 6.8
- Qt Widgets
- C++ Classes
- QDataWidgetMapper
- Qt 6.8.1 Reference Documentation

# QDataWidgetMapper Class

The QDataWidgetMapper class provides mapping between a section of a data model to widgets. More...

Header: | `#include <QDataWidgetMapper>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Widgets)` `target_link_libraries(mytarget PRIVATE Qt6::Widgets)`
qmake: | `QT += widgets`
Inherits: | QObject

- List of all members, including inherited members

## Public Types

enum | SubmitPolicy { AutoSubmit, ManualSubmit }

## Properties

- currentIndex : int
- orientation : Qt::Orientation
- submitPolicy : SubmitPolicy

## Public Functions

| QDataWidgetMapper(QObject *parent = nullptr)
virtual | ~QDataWidgetMapper()
void | addMapping(QWidget *widget, int section)
void | addMapping(QWidget *widget, int section, const QByteArray &propertyName)
void | clearMapping()
int | currentIndex() const
QAbstractItemDelegate * | itemDelegate() const
QByteArray | mappedPropertyName(QWidget *widget) const
int | mappedSection(QWidget *widget) const
QWidget * | mappedWidgetAt(int section) const
QAbstractItemModel * | model() const
Qt::Orientation | orientation() const
void | removeMapping(QWidget *widget)
QModelIndex | rootIndex() const
void | setItemDelegate(QAbstractItemDelegate *delegate)
void | setModel(QAbstractItemModel *model)
void | setOrientation(Qt::Orientation aOrientation)
void | setRootIndex(const QModelIndex &index)
void | setSubmitPolicy(QDataWidgetMapper::SubmitPolicy policy)
QDataWidgetMapper::SubmitPolicy | submitPolicy() const

## Public Slots

void | revert()
virtual void | setCurrentIndex(int index)
void | setCurrentModelIndex(const QModelIndex &index)
bool | submit()
void | toFirst()
void | toLast()
void | toNext()
void | toPrevious()

## Signals

void | currentIndexChanged(int index)

## Detailed Description

QDataWidgetMapper can be used to create data-aware widgets by mapping them to sections of an item model. A section is a column of a model if the orientation is horizontal (the default), otherwise a row.

Every time the current index changes, each widget is updated with data from the model via the property specified when its mapping was made. If the user edits the contents of a widget, the changes are read using the same property and written back to the model. By default, each widget's user property is used to transfer data between the model and the widget. Since Qt 4.3, an additional addMapping() function enables a named property to be used instead of the default user property.

It is possible to set an item delegate to support custom widgets. By default, a QStyledItemDelegate is used to synchronize the model with the widgets.

Let us assume that we have an item model named `model` with the following contents:

1 | Qt Norway | Oslo
2 | Qt Australia | Brisbane
3 | Qt USA | Palo Alto
4 | Qt China | Beijing
5 | Qt Germany | Berlin

The following code will map the columns of the model to widgets called `mySpinBox`, `myLineEdit` and `myCountryChooser`:

     QDataWidgetMapper *mapper = new QDataWidgetMapper;
     mapper->setModel(model);
     mapper->addMapping(mySpinBox, 0);
     mapper->addMapping(myLineEdit, 1);
     mapper->addMapping(myCountryChooser, 2);
     mapper->toFirst();

After the call to toFirst(), `mySpinBox` displays the value `1`, `myLineEdit` displays `Qt Norway` and `myCountryChooser` displays `Oslo`. The navigational functions toFirst(), toNext(), toPrevious(), toLast() and setCurrentIndex() can be used to navigate in the model and update the widgets with contents from the model.

The setRootIndex() function enables a particular item in a model to be specified as the root index - children of this item will be mapped to the relevant widgets in the user interface.

QDataWidgetMapper supports two submit policies, `AutoSubmit` and `ManualSubmit`. `AutoSubmit` will update the model as soon as the current widget loses focus, `ManualSubmit` will not update the model unless submit() is called. `ManualSubmit` is useful when displaying a dialog that lets the user cancel all modifications. Also, other views that display the model won't update until the user finishes all their modifications and submits.

Note that QDataWidgetMapper keeps track of external modifications. If the contents of the model are updated in another module of the application, the widgets are updated as well.

See also QAbstractItemModel and QAbstractItemDelegate.

## Member Type Documentation

### enum QDataWidgetMapper::SubmitPolicy

This enum describes the possible submit policies a QDataWidgetMapper supports.

Constant | Value | Description
--- | --- | ---
`QDataWidgetMapper::AutoSubmit` | `0` | Whenever a widget loses focus, the widget's current value is set to the item model.
`QDataWidgetMapper::ManualSubmit` | `1` | The model is not updated until submit() is called.

## Property Documentation

### currentIndex : int

This property holds the current row or column

The widgets are populated with with data from the row at index if the orientation is horizontal (the default), otherwise with data from the column at index.

Access functions:

int | currentIndex() const
virtual void | setCurrentIndex(int index)

Notifier signal:

void | currentIndexChanged(int index)

See also setCurrentModelIndex(), toFirst(), toNext(), toPrevious(), and toLast().

### orientation : Qt::Orientation

This property holds the orientation of the model

If the orientation is Qt::Horizontal (the default), a widget is mapped to a column of a data model. The widget will be populated with the model's data from its mapped column and the row that currentIndex() points at.

Use Qt::Horizontal for tabular data that looks like this:

1 | Qt Norway | Oslo
2 | Qt Australia | Brisbane
3 | Qt USA | Silicon Valley
4 | Qt China | Beijing
5 | Qt Germany | Berlin

If the orientation is set to Qt::Vertical, a widget is mapped to a row. Calling setCurrentIndex() will change the current column. The widget will be populates with the model's data from its mapped row and the column that currentIndex() points at.

Use Qt::Vertical for tabular data that looks like this:

1 | 2 | 3 | 4 | 5
Qt Norway | Qt Australia | Qt USA | Qt China | Qt Germany
Oslo | Brisbane | Silicon Valley | Beijing | Berlin

Changing the orientation clears all existing mappings.

Access functions:

Qt::Orientation | orientation() const
void | setOrientation(Qt::Orientation aOrientation)

### submitPolicy : SubmitPolicy

This property holds the current submit policy

Changing the current submit policy will revert all widgets to the current data from the model.

Access functions:

QDataWidgetMapper::SubmitPolicy | submitPolicy() const
void | setSubmitPolicy(QDataWidgetMapper::SubmitPolicy policy)

## Member Function Documentation

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

Constructs a new QDataWidgetMapper with parent object parent. By default, the orientation is horizontal and the submit policy is `AutoSubmit`.

See also setOrientation() and setSubmitPolicy().

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

Destroys the object.

### void QDataWidgetMapper::addMapping(QWidget *widget, int section)

Adds a mapping between a widget and a section from the model. The section is a column in the model if the orientation is horizontal (the default), otherwise a row.

For the following example, we assume a model `myModel` that has two columns: the first one contains the names of people in a group, and the second column contains their ages. The first column is mapped to the QLineEdit `nameLineEdit`, and the second is mapped to the QSpinBox `ageSpinBox`:

     QDataWidgetMapper *mapper = new QDataWidgetMapper;
     mapper->setModel(myModel);
     mapper->addMapping(nameLineEdit, 0);
     mapper->addMapping(ageSpinBox, 1);

Notes:

- If the widget is already mapped to a section, the old mapping will be replaced by the new one.
- Only one-to-one mappings between sections and widgets are allowed. It is not possible to map a single section to multiple widgets, or to map a single widget to multiple sections.

See also removeMapping(), mappedSection(), and clearMapping().

### void QDataWidgetMapper::addMapping(QWidget *widget, int section, const QByteArray &propertyName)

Essentially the same as addMapping(), but adds the possibility to specify the property to use specifying propertyName.

See also addMapping().

### void QDataWidgetMapper::clearMapping()

Clears all mappings.

See also addMapping() and removeMapping().

### `[signal]` void QDataWidgetMapper::currentIndexChanged(int index)

This signal is emitted after the current index has changed and all widgets were populated with new data. index is the new current index.

Note: Notifier signal for property currentIndex.

See also currentIndex() and setCurrentIndex().

### QAbstractItemDelegate *QDataWidgetMapper::itemDelegate() const

Returns the current item delegate.

See also setItemDelegate().

### QByteArray QDataWidgetMapper::mappedPropertyName(QWidget *widget) const

Returns the name of the property that is used when mapping data to the given widget.

See also mappedSection(), addMapping(), and removeMapping().

### int QDataWidgetMapper::mappedSection(QWidget *widget) const

Returns the section the widget is mapped to or -1 if the widget is not mapped.

See also addMapping() and removeMapping().

### QWidget *QDataWidgetMapper::mappedWidgetAt(int section) const

Returns the widget that is mapped at section, or 0 if no widget is mapped at that section.

See also addMapping() and removeMapping().

### QAbstractItemModel *QDataWidgetMapper::model() const

Returns the current model.

See also setModel().

### void QDataWidgetMapper::removeMapping(QWidget *widget)

Removes the mapping for the given widget.

See also addMapping() and clearMapping().

### `[slot]` void QDataWidgetMapper::revert()

Repopulates all widgets with the current data of the model. All unsubmitted changes will be lost.

See also submit() and setSubmitPolicy().

### QModelIndex QDataWidgetMapper::rootIndex() const

Returns the current root index.

See also setRootIndex().

### `[slot]` void QDataWidgetMapper::setCurrentModelIndex(const QModelIndex &index)

Sets the current index to the row of the index if the orientation is horizontal (the default), otherwise to the column of the index.

Calls setCurrentIndex() internally. This convenience slot can be connected to the signal currentRowChanged() or currentColumnChanged() of another view's selection model.

The following example illustrates how to update all widgets with new data whenever the selection of a QTableView named `myTableView` changes:

     QDataWidgetMapper *mapper = new QDataWidgetMapper;
     connect(myTableView->selectionModel(), &QItemSelectionModel::currentRowChanged,
             mapper, &QDataWidgetMapper::setCurrentModelIndex);

See also currentIndex().

### void QDataWidgetMapper::setItemDelegate(QAbstractItemDelegate *delegate)

Sets the item delegate to delegate. The delegate will be used to write data from the model into the widget and from the widget to the model, using QAbstractItemDelegate::setEditorData() and QAbstractItemDelegate::setModelData().

Any existing delegate will be removed, but not deleted. QDataWidgetMapper does not take ownership of delegate.

The delegate also decides when to apply data and when to change the editor, using QAbstractItemDelegate::commitData() and QAbstractItemDelegate::closeEditor().

Warning: You should not share the same instance of a delegate between widget mappers or views. Doing so can cause incorrect or unintuitive editing behavior since each view connected to a given delegate may receive the closeEditor() signal, and attempt to access, modify or close an editor that has already been closed.

See also itemDelegate().

### void QDataWidgetMapper::setModel(QAbstractItemModel *model)

Sets the current model to model. If another model was set, all mappings to that old model are cleared.

See also model().

### void QDataWidgetMapper::setRootIndex(const QModelIndex &index)

Sets the root item to index. This can be used to display a branch of a tree. Pass an invalid model index to display the top-most branch.

See also rootIndex().

### `[slot]` bool QDataWidgetMapper::submit()

Submits all changes from the mapped widgets to the model.

For every mapped section, the item delegate reads the current value from the widget and sets it in the model. Finally, the model's submit() method is invoked.

Returns `true` if all the values were submitted, otherwise false.

Note: For database models, QSqlQueryModel::lastError() can be used to retrieve the last error.

See also revert() and setSubmitPolicy().

### `[slot]` void QDataWidgetMapper::toFirst()

Populates the widgets with data from the first row of the model if the orientation is horizontal (the default), otherwise with data from the first column.

This is equivalent to calling `setCurrentIndex(0)`.

See also toLast() and setCurrentIndex().

### `[slot]` void QDataWidgetMapper::toLast()

Populates the widgets with data from the last row of the model if the orientation is horizontal (the default), otherwise with data from the last column.

Calls setCurrentIndex() internally.

See also toFirst() and setCurrentIndex().

### `[slot]` void QDataWidgetMapper::toNext()

Populates the widgets with data from the next row of the model if the orientation is horizontal (the default), otherwise with data from the next column.

Calls setCurrentIndex() internally. Does nothing if there is no next row in the model.

See also toPrevious() and setCurrentIndex().

### `[slot]` void QDataWidgetMapper::toPrevious()

Populates the widgets with data from the previous row of the model if the orientation is horizontal (the default), otherwise with data from the previous column.

Calls setCurrentIndex() internally. Does nothing if there is no previous row in the model.

See also toNext() and setCurrentIndex().