The QgsDefaultValue class provides a container for managing client side default values for fields. More...

#include <qgsdefaultvalue.h>

Public Member Functions
	QgsDefaultValue (const QString &expression=QString(), bool applyOnUpdate=false)
	Create a new default value with the given expression and applyOnUpdate flag. More...

bool	applyOnUpdate () const
	The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it's created. More...

QString	expression () const
	The expression will be evaluated whenever a default value needs to be calculated for a field. More...

bool	isValid () const
	Returns if this default value should be applied. More...

	operator bool () const SIP_PYTHON_SPECIAL_BOOL(isValid)
	Checks if a default value is set. More...

bool	operator== (const QgsDefaultValue &other) const

void	setApplyOnUpdate (bool applyOnUpdate)
	The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it's created. More...

void	setExpression (const QString &expression)
	The expression will be evaluated whenever a default value needs to be calculated for a field. More...

Properties
bool	applyOnUpdate

Q_GADGET QString	expression

Detailed Description

The QgsDefaultValue class provides a container for managing client side default values for fields.

A QgsDefaultValue consists of an expression string that will be evaluated on the client when a default field value needs to be generated.

Usual values for such an expression are

now() for a timestamp for a record
@some_variable to insert a project or application level variable like the username of the one digitizing a feature
$length to insert a derived attribute of a geometry

QgsDefaultValue also has a applyOnUpdate flag which will indicate that a default value should also be applied when a feature is updated. If this is not set, the default value will only be used when a feature is created.

Since: QGIS 3.0

Definition at line 48 of file qgsdefaultvalue.h.

Constructor & Destructor Documentation

◆ QgsDefaultValue()

QgsDefaultValue::QgsDefaultValue	(	const QString &	expression = `QString()`,
		bool	applyOnUpdate = `false`
	)

explicit

Create a new default value with the given expression and applyOnUpdate flag.

See also: QgsVectorLayer::setDefaultValueDefinition

Definition at line 18 of file qgsdefaultvalue.cpp.

Member Function Documentation

◆ applyOnUpdate()

bool QgsDefaultValue::applyOnUpdate ( ) const

The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it's created.

Definition at line 41 of file qgsdefaultvalue.cpp.

◆ expression()

QString QgsDefaultValue::expression ( ) const

The expression will be evaluated whenever a default value needs to be calculated for a field.

Definition at line 31 of file qgsdefaultvalue.cpp.

◆ isValid()

bool QgsDefaultValue::isValid ( ) const

Returns if this default value should be applied.

Returns: false if the expression is a null string.

Definition at line 51 of file qgsdefaultvalue.cpp.

◆ operator bool()

QgsDefaultValue::operator bool ( ) const

Checks if a default value is set.

Alias for isValid().

Returns: false if the expression is a null string.

Definition at line 56 of file qgsdefaultvalue.cpp.

◆ operator==()

bool QgsDefaultValue::operator== ( const QgsDefaultValue & other ) const

Definition at line 25 of file qgsdefaultvalue.cpp.

◆ setApplyOnUpdate()

void QgsDefaultValue::setApplyOnUpdate ( bool applyOnUpdate )

The applyOnUpdate flag determines if this expression should also be applied when a feature is updated or only when it's created.

Definition at line 46 of file qgsdefaultvalue.cpp.

◆ setExpression()

void QgsDefaultValue::setExpression ( const QString & expression )

The expression will be evaluated whenever a default value needs to be calculated for a field.

Definition at line 36 of file qgsdefaultvalue.cpp.

Property Documentation

◆ applyOnUpdate

bool QgsDefaultValue::applyOnUpdate

readwrite

Definition at line 50 of file qgsdefaultvalue.h.

◆ expression

Q_GADGET QString QgsDefaultValue::expression