Contains utility methods for working with QgsVectorLayers. More...

#include <qgsvectorlayerutils.h>

Classes
class	QgsDuplicateFeatureContext
	Contains mainly the QMap with QgsVectorLayer and QgsFeatureIds do list all the duplicated features. More...

Static Public Member Functions
static QgsFeature	createFeature (const QgsVectorLayer layer, const QgsGeometry &geometry=QgsGeometry(), const QgsAttributeMap &attributes=QgsAttributeMap(), QgsExpressionContext context=nullptr)
	Creates a new feature ready for insertion into a layer. More...

static QVariant	createUniqueValue (const QgsVectorLayer *layer, int fieldIndex, const QVariant &seed=QVariant())
	Returns a new attribute value for the specified field index which is guaranteed to be unique. More...

static QgsFeature	duplicateFeature (QgsVectorLayer layer, const QgsFeature &feature, QgsProject project, int depth, QgsDuplicateFeatureContext &duplicateFeatureContext)
	Duplicates a feature and it's children (one level deep). More...

static QList< double >	getDoubleValues (const QgsVectorLayer layer, const QString &fieldOrExpression, bool &ok, bool selectedOnly=false, int nullCount=nullptr, QgsFeedback *feedback=nullptr)
	Fetches all double values from a specified field name or expression. More...

static std::unique_ptr< QgsVectorLayerFeatureSource >	getFeatureSource (QPointer< QgsVectorLayer > layer, QgsFeedback *feedback=nullptr)
	Gets the feature source from a QgsVectorLayer pointer. More...

static QList< QVariant >	getValues (const QgsVectorLayer layer, const QString &fieldOrExpression, bool &ok, bool selectedOnly=false, QgsFeedback feedback=nullptr)
	Fetches all values from a specified field name or expression. More...

static QgsFeatureIterator	getValuesIterator (const QgsVectorLayer *layer, const QString &fieldOrExpression, bool &ok, bool selectedOnly)
	Create a feature iterator for a specified field name or expression. More...

static QgsFeatureList	makeFeatureCompatible (const QgsFeature &feature, const QgsVectorLayer *layer)
	Converts input feature to be compatible with the given layer. More...

static QgsFeatureList	makeFeaturesCompatible (const QgsFeatureList &features, const QgsVectorLayer *layer)
	Converts input features to be compatible with the given layer. More...

static void	matchAttributesToFields (QgsFeature &feature, const QgsFields &fields)
	Matches the attributes in feature to the specified fields. More...

static bool	validateAttribute (const QgsVectorLayer *layer, const QgsFeature &feature, int attributeIndex, QStringList &errors, QgsFieldConstraints::ConstraintStrength strength=QgsFieldConstraints::ConstraintStrengthNotSet, QgsFieldConstraints::ConstraintOrigin origin=QgsFieldConstraints::ConstraintOriginNotSet)
	Tests an attribute value to check whether it passes all constraints which are present on the corresponding field. More...

static bool	valueExists (const QgsVectorLayer *layer, int fieldIndex, const QVariant &value, const QgsFeatureIds &ignoreIds=QgsFeatureIds())
	Returns true if the specified value already exists within a field. More...

Detailed Description

Contains utility methods for working with QgsVectorLayers.

Since: QGIS 3.0

Definition at line 31 of file qgsvectorlayerutils.h.

Member Function Documentation

QgsFeature QgsVectorLayerUtils::createFeature	(	const QgsVectorLayer *	layer,
		const QgsGeometry &	geometry = `QgsGeometry()`,
		const QgsAttributeMap &	attributes = `QgsAttributeMap()`,
		QgsExpressionContext *	context = `nullptr`
	)

static

Creates a new feature ready for insertion into a layer.

Default values and constraints (e.g., unique constraints) will automatically be handled. An optional attribute map can be passed for the new feature to copy as many attribute values as possible from the map, assuming that they respect the layer's constraints. Note that the created feature is not automatically inserted into the layer.

Definition at line 358 of file qgsvectorlayerutils.cpp.

QVariant QgsVectorLayerUtils::createUniqueValue	(	const QgsVectorLayer *	layer,
		int	fieldIndex,
		const QVariant &	seed = `QVariant()`
	)

static

Returns a new attribute value for the specified field index which is guaranteed to be unique.

The optional seed value can be used as a basis for generated values.

See also: valueExists()

Definition at line 186 of file qgsvectorlayerutils.cpp.

QgsFeature QgsVectorLayerUtils::duplicateFeature	(	QgsVectorLayer *	layer,
		const QgsFeature &	feature,
		QgsProject *	project,
		int	depth,
		QgsDuplicateFeatureContext &	duplicateFeatureContext
	)

static

Duplicates a feature and it's children (one level deep).

It calls CreateFeature, so default values and constraints (e.g., unique constraints) will automatically be handled. The duplicated feature will be automatically inserted into the layer. depth the higher this number the deeper the level - With depth > 0 the children of the feature are not duplicated duplicateFeatureContext stores all the layers and the featureids of the duplicated features (incl. children)

Since: QGIS 3.0

Definition at line 462 of file qgsvectorlayerutils.cpp.

QList< double > QgsVectorLayerUtils::getDoubleValues	(	const QgsVectorLayer *	layer,
		const QString &	fieldOrExpression,
		bool &	ok,
		bool	selectedOnly = `false`,
		int *	nullCount = `nullptr`,
		QgsFeedback *	feedback = `nullptr`
	)

static

Fetches all double values from a specified field name or expression.

Null values or invalid expression results are skipped.

Parameters

layer	vector layer to retrieve values from
fieldOrExpression	field name or an expression string evaluating to a double value
ok	will be set to false if field or expression is invalid, otherwise true
selectedOnly	set to true to get values from selected features only
nullCount	optional pointer to integer to store number of null values encountered in
feedback	optional feedback object to allow cancellation

Returns: list of fetched values

See also: getValues

Since: QGIS 3.0

Definition at line 118 of file qgsvectorlayerutils.cpp.

std::unique_ptr< QgsVectorLayerFeatureSource > QgsVectorLayerUtils::getFeatureSource	(	QPointer< QgsVectorLayer >	layer,
		QgsFeedback *	feedback = `nullptr`
	)

static

Gets the feature source from a QgsVectorLayer pointer.

This method is thread-safe but will block the main thread for execution. Executing it from the main thread is safe too. This should be used in scenarios, where a QWeakPointer<QgsVectorLayer> is kept in a thread and features should be fetched from this layer. Using the layer directly is not safe to do. The result will be nullptr if the layer has been deleted. If feedback is specified, the call will return if the feedback is canceled. Returns a new feature source for the layer. The source may be a nullptr if the layer no longer exists or if the feedback is canceled.

Note: Requires Qt >= 5.10 to make use of the thread-safe implementation

Since: QGIS 3.4

Definition at line 512 of file qgsvectorlayerutils.cpp.

QList< QVariant > QgsVectorLayerUtils::getValues	(	const QgsVectorLayer *	layer,
		const QString &	fieldOrExpression,
		bool &	ok,
		bool	selectedOnly = `false`,
		QgsFeedback *	feedback = `nullptr`
	)

static

Fetches all values from a specified field name or expression.

Parameters

layer	vector layer to retrieve values from
fieldOrExpression	field name or an expression string
ok	will be set to false if field or expression is invalid, otherwise true
selectedOnly	set to true to get values from selected features only
feedback	optional feedback object to allow cancellation

Returns: list of fetched values

See also: getDoubleValues

Since: QGIS 3.0

Definition at line 78 of file qgsvectorlayerutils.cpp.

QgsFeatureIterator QgsVectorLayerUtils::getValuesIterator	(	const QgsVectorLayer *	layer,
		const QString &	fieldOrExpression,
		bool &	ok,
		bool	selectedOnly
	)

static

Create a feature iterator for a specified field name or expression.

Parameters

layer	vector layer to retrieve values from
fieldOrExpression	field name or an expression string
ok	will be set to false if field or expression is invalid, otherwise true
selectedOnly	set to true to get values from selected features only

Returns: feature iterator

Since: QGIS 3.0

Definition at line 36 of file qgsvectorlayerutils.cpp.

QgsFeatureList QgsVectorLayerUtils::makeFeatureCompatible	(	const QgsFeature &	feature,
		const QgsVectorLayer *	layer
	)

static

Converts input feature to be compatible with the given layer.

This function returns a new list of transformed features compatible with the input layer, note that the number of features returned might be greater than one when converting a multi part geometry to single part

The following operations will be performed to convert the input features:

convert single geometries to multi part
drop additional attributes
drop geometry if layer is geometry-less
add missing attribute fields
add back M/Z values (initialized to 0)
drop Z/M
convert multi part geometries to single part

Since: QGIS 3.4

Definition at line 574 of file qgsvectorlayerutils.cpp.

QgsFeatureList QgsVectorLayerUtils::makeFeaturesCompatible	(	const QgsFeatureList &	features,
		const QgsVectorLayer *	layer
	)

static

Converts input features to be compatible with the given layer.

This function returns a new list of transformed features compatible with the input layer, note that the number of features returned might be greater than the number of input features.

The following operations will be performed to convert the input features:

convert single geometries to multi part
drop additional attributes
drop geometry if layer is geometry-less
add missing attribute fields
add back M/Z values (initialized to 0)
drop Z/M
convert multi part geometries to single part

Since: QGIS 3.4

Definition at line 731 of file qgsvectorlayerutils.cpp.

void QgsVectorLayerUtils::matchAttributesToFields	(	QgsFeature &	feature,
		const QgsFields &	fields
	)

static

Matches the attributes in feature to the specified fields.

This causes the attributes contained within the given feature to be rearranged (or in some cases dropped) in order to match the fields and order indicated by fields.

The exact behavior depends on whether or not feature has a valid fields container set (see QgsFeature::fields()). If a fields container is set, then the names of the feature's fields are matched to fields. In this case attributes from feature will be rearranged or dropped in order to match the field names from fields.

If the feature does not have a valid fields container set, then the feature's attributes are simply truncated to match the number of fields present in fields (or if less attributes are present in feature than in fields, the feature's attributes are padded with NULL values to match the required length).

Since: QGIS 3.4

Definition at line 536 of file qgsvectorlayerutils.cpp.

bool QgsVectorLayerUtils::validateAttribute	(	const QgsVectorLayer *	layer,
		const QgsFeature &	feature,
		int	attributeIndex,
		QStringList &	errors,
		QgsFieldConstraints::ConstraintStrength	strength = `QgsFieldConstraints::ConstraintStrengthNotSet`,
		QgsFieldConstraints::ConstraintOrigin	origin = `QgsFieldConstraints::ConstraintOriginNotSet`
	)

static

Tests an attribute value to check whether it passes all constraints which are present on the corresponding field.

Returns true if the attribute value is valid for the field. Any constraint failures will be reported in the errors argument. If the strength or origin parameter is set then only constraints with a matching strength/origin will be checked.

Definition at line 266 of file qgsvectorlayerutils.cpp.

bool QgsVectorLayerUtils::valueExists	(	const QgsVectorLayer *	layer,
		int	fieldIndex,
		const QVariant &	value,
		const QgsFeatureIds &	ignoreIds = `QgsFeatureIds()`
	)

static

Returns true if the specified value already exists within a field.

This method can be used to test for uniqueness of values inside a layer's attributes. An optional list of ignored feature IDs can be provided, if so, any features with IDs within this list are ignored when testing for existence of the value.

See also: createUniqueValue()

Definition at line 149 of file qgsvectorlayerutils.cpp.

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

/build/qgis-3.4.15+24xenial/src/core/qgsvectorlayerutils.h
/build/qgis-3.4.15+24xenial/src/core/qgsvectorlayerutils.cpp

Classes

Static Public Member Functions

Detailed Description

Member Function Documentation