The QgsFieldExpressionWidget class creates a widget to choose fields and edit expressions It contains a combo box to display the fields and expression and a button to open the expression dialog. More...

#include <qgsfieldexpressionwidget.h>

Inheritance diagram for QgsFieldExpressionWidget:

[legend]

Public Slots
void	setExpression (const QString &expression)
	Sets the current expression text and if applicable also the field.

void	setField (const QString &fieldName)
	sets the current field or expression in the widget

void	setFields (const QgsFields &fields)
	Sets the fields used in the widget to fields, this allows the widget to work without a layer.

void	setLayer (QgsMapLayer *layer)
	Sets the layer used to display the fields and expression.

void	setRow (int row)
	sets the current row in the widget

Signals
void	allowEvalErrorsChanged ()
	Allow accepting expressions with evaluation errors.

void	buttonVisibleChanged ()
	Emitted when the button visibility changes.

void	fieldChanged (const QString &fieldName)
	Emitted when the currently selected field changes.

void	fieldChanged (const QString &fieldName, bool isValid)
	fieldChanged signal with indication of the validity of the expression

Public Member Functions
	QgsFieldExpressionWidget (QWidget *parent=nullptr)
	QgsFieldExpressionWidget creates a widget with a combo box to display the fields and expression and a button to open the expression dialog.

bool	allowEmptyFieldName () const
	Returns `true` if the combo box allows the empty field ("not set") choice.

bool	allowEvalErrors () const
	Allow accepting expressions with evaluation errors.

void	appendScope (QgsExpressionContextScope *scope)
	Appends a scope to the current expression context.

QString	asExpression () const
	Returns the currently selected field or expression.

bool	buttonVisible () const
	Returns the visibility of the button.

QString	currentField (bool isExpression=nullptr, bool isValid=nullptr) const
	currentField returns the currently selected field or expression if allowed

QString	currentText () const
	Returns the current text that is set in the expression area.

QString	expression () const
	Returns the currently selected field or expression.

const QString	expressionDialogTitle ()
	Returns the title used for the expression dialog.

QgsFieldProxyModel::Filters	filters () const
	currently used filter on list of fields

bool	isExpression () const
	If the content is not just a simple field this method will return `true`.

bool	isValidExpression (QString *expressionError=nullptr) const
	Returns `true` if the current expression is valid.

QgsVectorLayer *	layer () const
	Returns the layer currently associated with the widget.

void	registerExpressionContextGenerator (const QgsExpressionContextGenerator *generator)
	Register an expression context generator class that will be used to retrieve an expression context for the widget.

void	setAllowEmptyFieldName (bool allowEmpty)
	Sets whether an optional empty field ("not set") option is shown in the combo box.

void	setAllowEvalErrors (bool allowEvalErrors)
	Allow accepting expressions with evaluation errors.

void	setButtonVisible (bool visible)
	Set the visibility of the button.

void	setCustomPreviewGenerator (const QString &label, const QList< QPair< QString, QVariant > > &choices, const std::function< QgsExpressionContext(const QVariant &)> &previewContextGenerator)
	Sets the widget to run using a custom preview generator.

void	setExpressionDialogTitle (const QString &title)
	define the title used in the expression dialog

void	setFilters (QgsFieldProxyModel::Filters filters)
	setFilters allows filtering according to the type of field

void	setGeomCalculator (const QgsDistanceArea &da)
	Sets the geometry calculator used in the expression dialog.

void	setLeftHandButtonStyle (bool isLeft)

Protected Slots
void	currentFieldChanged ()

void	editExpression ()
	open the expression dialog to edit the current or add a new expression

void	expressionEdited (const QString &expression)
	when expression is edited by the user in the line edit, it will be checked for validity

void	expressionEditingFinished ()
	when expression has been edited (finished) it will be added to the model

bool	isExpressionValid (const QString &expressionStr)

void	updateLineEditStyle (const QString &expression=QString())
	updateLineEditStyle will re-style (color/font) the line edit depending on content and status

Protected Member Functions
void	changeEvent (QEvent *event) override

bool	eventFilter (QObject watched, QEvent event) override

Properties
bool	allowEmptyFieldName

bool	allowEvalErrors

bool	buttonVisible

QString	expressionDialogTitle

QgsFieldProxyModel::Filters	filters

Friends
class	TestQgsFieldExpressionWidget

Detailed Description

The QgsFieldExpressionWidget class creates a widget to choose fields and edit expressions It contains a combo box to display the fields and expression and a button to open the expression dialog.

The combo box is editable, allowing expressions to be edited inline. The validity of the expression is checked live on key press, invalid expressions are displayed in red. The expression will be added to the model (and the fieldChanged signals emitted) only when editing in the line edit is finished (focus lost, enter key pressed).

Definition at line 46 of file qgsfieldexpressionwidget.h.

Constructor & Destructor Documentation

◆ QgsFieldExpressionWidget()

QgsFieldExpressionWidget::QgsFieldExpressionWidget ( QWidget * parent = nullptr )

explicit

QgsFieldExpressionWidget creates a widget with a combo box to display the fields and expression and a button to open the expression dialog.

Definition at line 33 of file qgsfieldexpressionwidget.cpp.

Member Function Documentation

◆ allowEmptyFieldName()

bool QgsFieldExpressionWidget::allowEmptyFieldName ( ) const

Returns true if the combo box allows the empty field ("not set") choice.

See also: setAllowEmptyFieldName()

Since: QGIS 3.4.6

Definition at line 89 of file qgsfieldexpressionwidget.cpp.

◆ allowEvalErrors()

bool QgsFieldExpressionWidget::allowEvalErrors ( ) const

Allow accepting expressions with evaluation errors.

This can be useful when we are not able to provide an expression context of which we are sure it's completely populated.

Definition at line 324 of file qgsfieldexpressionwidget.cpp.

◆ allowEvalErrorsChanged

void QgsFieldExpressionWidget::allowEvalErrorsChanged ( )

signal

Allow accepting expressions with evaluation errors.

This can be useful when we are not able to provide an expression context of which we are sure it's completely populated.

◆ appendScope()

void QgsFieldExpressionWidget::appendScope ( QgsExpressionContextScope * scope )

Appends a scope to the current expression context.

Parameters

scope The scope to add.

Since: QGIS 3.2

Definition at line 414 of file qgsfieldexpressionwidget.cpp.

◆ asExpression()

QString QgsFieldExpressionWidget::asExpression ( ) const

Returns the currently selected field or expression.

If a field is currently selected, the returned value will be converted to a valid expression referencing this field (ie enclosing the field name with appropriate quotations).

Definition at line 119 of file qgsfieldexpressionwidget.cpp.

◆ buttonVisible()

bool QgsFieldExpressionWidget::buttonVisible ( ) const

Returns the visibility of the button.

If button is hidden, the widget essentially becomes an editable combo box

Since: QGIS 3.36

Definition at line 339 of file qgsfieldexpressionwidget.cpp.

◆ buttonVisibleChanged

void QgsFieldExpressionWidget::buttonVisibleChanged ( )

signal

Emitted when the button visibility changes.

Since: QGIS 3.36

◆ changeEvent()

void QgsFieldExpressionWidget::changeEvent ( QEvent * event )

overrideprotected

Definition at line 285 of file qgsfieldexpressionwidget.cpp.

◆ currentField()

QString QgsFieldExpressionWidget::currentField	(	bool *	isExpression = `nullptr`,
		bool *	isValid = `nullptr`
	)		const

currentField returns the currently selected field or expression if allowed

Parameters

isExpression	determines if the string returned is the name of a field or an expression
isValid	determines if the expression (or field) returned is valid

Definition at line 140 of file qgsfieldexpressionwidget.cpp.

◆ currentFieldChanged

void QgsFieldExpressionWidget::currentFieldChanged ( )

protectedslot

Definition at line 353 of file qgsfieldexpressionwidget.cpp.

◆ currentText()

QString QgsFieldExpressionWidget::currentText ( ) const

Returns the current text that is set in the expression area.

Definition at line 114 of file qgsfieldexpressionwidget.cpp.

◆ editExpression

void QgsFieldExpressionWidget::editExpression ( )

protectedslot

open the expression dialog to edit the current or add a new expression

Definition at line 239 of file qgsfieldexpressionwidget.cpp.

◆ eventFilter()

bool QgsFieldExpressionWidget::eventFilter	(	QObject *	watched,
		QEvent *	event
	)

overrideprotected

Definition at line 310 of file qgsfieldexpressionwidget.cpp.

◆ expression()

QString QgsFieldExpressionWidget::expression ( ) const

Returns the currently selected field or expression.

If a field is currently selected, the returned value will be converted to a valid expression referencing this field (ie enclosing the field name with appropriate quotations).

Alias for asExpression()

Definition at line 124 of file qgsfieldexpressionwidget.cpp.

◆ expressionDialogTitle()

const QString QgsFieldExpressionWidget::expressionDialogTitle ( )

inline

Returns the title used for the expression dialog.

Definition at line 74 of file qgsfieldexpressionwidget.h.

◆ expressionEdited

void QgsFieldExpressionWidget::expressionEdited ( const QString & expression )

protectedslot

when expression is edited by the user in the line edit, it will be checked for validity

Definition at line 269 of file qgsfieldexpressionwidget.cpp.

◆ expressionEditingFinished

void QgsFieldExpressionWidget::expressionEditingFinished ( )

protectedslot

when expression has been edited (finished) it will be added to the model

Definition at line 275 of file qgsfieldexpressionwidget.cpp.

◆ fieldChanged [1/2]

void QgsFieldExpressionWidget::fieldChanged ( const QString & fieldName )

signal

Emitted when the currently selected field changes.

◆ fieldChanged [2/2]

void QgsFieldExpressionWidget::fieldChanged	(	const QString &	fieldName,
		bool	isValid
	)

signal

fieldChanged signal with indication of the validity of the expression

◆ filters()

QgsFieldProxyModel::Filters QgsFieldExpressionWidget::filters ( ) const

inline

currently used filter on list of fields

Definition at line 96 of file qgsfieldexpressionwidget.h.

◆ isExpression()

bool QgsFieldExpressionWidget::isExpression ( ) const

If the content is not just a simple field this method will return true.

Definition at line 135 of file qgsfieldexpressionwidget.cpp.

◆ isExpressionValid

bool QgsFieldExpressionWidget::isExpressionValid ( const QString & expressionStr )

protectedslot

Definition at line 407 of file qgsfieldexpressionwidget.cpp.

◆ isValidExpression()

bool QgsFieldExpressionWidget::isValidExpression ( QString * expressionError = nullptr ) const

Returns true if the current expression is valid.

Definition at line 129 of file qgsfieldexpressionwidget.cpp.

◆ layer()

QgsVectorLayer * QgsFieldExpressionWidget::layer ( ) const

Returns the layer currently associated with the widget.

See also: setLayer()

Definition at line 156 of file qgsfieldexpressionwidget.cpp.

◆ registerExpressionContextGenerator()

void QgsFieldExpressionWidget::registerExpressionContextGenerator ( const QgsExpressionContextGenerator * generator )

Register an expression context generator class that will be used to retrieve an expression context for the widget.

Parameters

generator A QgsExpressionContextGenerator class that will be used to create an expression context when required.

Definition at line 161 of file qgsfieldexpressionwidget.cpp.

◆ setAllowEmptyFieldName()

void QgsFieldExpressionWidget::setAllowEmptyFieldName ( bool allowEmpty )

Sets whether an optional empty field ("not set") option is shown in the combo box.

See also: allowEmptyFieldName()

Since: QGIS 3.4.6

Definition at line 83 of file qgsfieldexpressionwidget.cpp.

◆ setAllowEvalErrors()

void QgsFieldExpressionWidget::setAllowEvalErrors ( bool allowEvalErrors )

Allow accepting expressions with evaluation errors.

This can be useful when we are not able to provide an expression context of which we are sure it's completely populated.

Definition at line 329 of file qgsfieldexpressionwidget.cpp.

◆ setButtonVisible()

void QgsFieldExpressionWidget::setButtonVisible ( bool visible )

Set the visibility of the button.

If button is hidden, the widget essentially becomes an editable combo box

Since: QGIS 3.36

Definition at line 344 of file qgsfieldexpressionwidget.cpp.

◆ setCustomPreviewGenerator()

void QgsFieldExpressionWidget::setCustomPreviewGenerator	(	const QString &	label,
		const QList< QPair< QString, QVariant > > &	choices,
		const std::function< QgsExpressionContext(const QVariant &)> &	previewContextGenerator
	)

Sets the widget to run using a custom preview generator.

In this mode, the widget will call a callback function to generate a new QgsExpressionContext as the previewed object changes. This can be used to provide custom preview values for different objects (i.e. for objects which aren't vector layer features).

Parameters

label	The label to display for the combo box presenting choices of objects. This should be a representative name, eg "Band" if the widget is showing choices of raster layer bands
choices	A list of choices to present to the user. Each choice is a pair of a human-readable label and a QVariant representing the object to preview.
previewContextGenerator	A function which takes a QVariant representing the object to preview, and returns a QgsExpressionContext to use for previewing the object.

Since: QGIS 3.38

Definition at line 166 of file qgsfieldexpressionwidget.cpp.

◆ setExpression

void QgsFieldExpressionWidget::setExpression ( const QString & expression )

slot

Sets the current expression text and if applicable also the field.

Alias for setField.

Definition at line 234 of file qgsfieldexpressionwidget.cpp.

◆ setExpressionDialogTitle()

void QgsFieldExpressionWidget::setExpressionDialogTitle ( const QString & title )

define the title used in the expression dialog

Definition at line 73 of file qgsfieldexpressionwidget.cpp.

◆ setField

void QgsFieldExpressionWidget::setField ( const QString & fieldName )

slot

sets the current field or expression in the widget

Definition at line 191 of file qgsfieldexpressionwidget.cpp.

◆ setFields

void QgsFieldExpressionWidget::setFields ( const QgsFields & fields )

slot

Sets the fields used in the widget to fields, this allows the widget to work without a layer.

Since: QGIS 3.14

Definition at line 229 of file qgsfieldexpressionwidget.cpp.

◆ setFilters()

void QgsFieldExpressionWidget::setFilters ( QgsFieldProxyModel::Filters filters )

setFilters allows filtering according to the type of field

Definition at line 78 of file qgsfieldexpressionwidget.cpp.

◆ setGeomCalculator()

void QgsFieldExpressionWidget::setGeomCalculator ( const QgsDistanceArea & da )

Sets the geometry calculator used in the expression dialog.

Definition at line 109 of file qgsfieldexpressionwidget.cpp.

◆ setLayer

void QgsFieldExpressionWidget::setLayer ( QgsMapLayer * layer )

slot

Sets the layer used to display the fields and expression.

See also: layer()

Definition at line 173 of file qgsfieldexpressionwidget.cpp.

◆ setLeftHandButtonStyle()

void QgsFieldExpressionWidget::setLeftHandButtonStyle ( bool isLeft )

Definition at line 94 of file qgsfieldexpressionwidget.cpp.

◆ setRow

void QgsFieldExpressionWidget::setRow ( int row )

inlineslot

sets the current row in the widget

Definition at line 271 of file qgsfieldexpressionwidget.h.

◆ updateLineEditStyle

void QgsFieldExpressionWidget::updateLineEditStyle ( const QString & expression = QString() )

protectedslot

updateLineEditStyle will re-style (color/font) the line edit depending on content and status

Parameters

expression if expression is given it will be evaluated for the given string, otherwise it takes current expression from the model

Definition at line 375 of file qgsfieldexpressionwidget.cpp.

Friends And Related Symbol Documentation

◆ TestQgsFieldExpressionWidget

friend class TestQgsFieldExpressionWidget

friend

Definition at line 336 of file qgsfieldexpressionwidget.h.

Property Documentation

◆ allowEmptyFieldName

bool QgsFieldExpressionWidget::allowEmptyFieldName

readwrite

Definition at line 51 of file qgsfieldexpressionwidget.h.

◆ allowEvalErrors

bool QgsFieldExpressionWidget::allowEvalErrors

readwrite

Definition at line 52 of file qgsfieldexpressionwidget.h.

◆ buttonVisible

bool QgsFieldExpressionWidget::buttonVisible

readwrite

Definition at line 53 of file qgsfieldexpressionwidget.h.

◆ expressionDialogTitle

QString QgsFieldExpressionWidget::expressionDialogTitle

readwrite

Definition at line 49 of file qgsfieldexpressionwidget.h.

◆ filters

QgsFieldProxyModel::Filters QgsFieldExpressionWidget::filters

readwrite

Definition at line 50 of file qgsfieldexpressionwidget.h.

The documentation for this class was generated from the following files:

/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/gui/qgsfieldexpressionwidget.h
/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/gui/qgsfieldexpressionwidget.cpp

Public Slots

Signals

Public Member Functions

Protected Slots

Protected Member Functions

Properties

Friends

Detailed Description

Constructor & Destructor Documentation

◆ QgsFieldExpressionWidget()

Member Function Documentation

◆ allowEmptyFieldName()

◆ allowEvalErrors()

◆ allowEvalErrorsChanged

◆ appendScope()

◆ asExpression()

◆ buttonVisible()

◆ buttonVisibleChanged

◆ changeEvent()

◆ currentField()

◆ currentFieldChanged

◆ currentText()

◆ editExpression

◆ eventFilter()

◆ expression()

◆ expressionDialogTitle()

◆ expressionEdited

◆ expressionEditingFinished

◆ fieldChanged [1/2]

◆ fieldChanged [2/2]

◆ filters()

◆ isExpression()

◆ isExpressionValid

◆ isValidExpression()

◆ layer()

◆ registerExpressionContextGenerator()

◆ setAllowEmptyFieldName()

◆ setAllowEvalErrors()

◆ setButtonVisible()

◆ setCustomPreviewGenerator()

◆ setExpression

◆ setExpressionDialogTitle()

◆ setField

◆ setFields

◆ setFilters()

◆ setGeomCalculator()

◆ setLayer

◆ setLeftHandButtonStyle()

◆ setRow

◆ updateLineEditStyle

Friends And Related Symbol Documentation

◆ TestQgsFieldExpressionWidget

Property Documentation

◆ allowEmptyFieldName

◆ allowEvalErrors

◆ buttonVisible

◆ expressionDialogTitle

◆ filters