An interface for objects which provide features via a getFeatures method. More...

#include <qgsfeaturesource.h>

Inheritance diagram for QgsFeatureSource:

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Public Types
enum	FeatureAvailability { NoFeaturesAvailable, FeaturesAvailable, FeaturesMaybeAvailable }
	Possible return value for hasFeatures() to determine if a source is empty. More...

Public Member Functions
virtual	~QgsFeatureSource ()=default

virtual QgsFeatureIds	allFeatureIds () const
	Returns a list of all feature IDs for features present in the source. More...

virtual long	featureCount () const =0
	Returns the number of features contained in the source, or -1 if the feature count is unknown. More...

virtual QgsFields	fields () const =0
	Returns the fields associated with features in the source. More...

virtual QgsFeatureIterator	getFeatures (const QgsFeatureRequest &request=QgsFeatureRequest()) const =0
	Returns an iterator for the features in the source. More...

virtual FeatureAvailability	hasFeatures () const
	Determines if there are any features available in the source. More...

QgsVectorLayer *	materialize (const QgsFeatureRequest &request, QgsFeedback *feedback=nullptr)
	Materializes a request (query) made against this feature source, by running it over the source and returning a new memory based vector layer containing the result. More...

virtual QVariant	maximumValue (int fieldIndex) const
	Returns the maximum value for an attribute column or an invalid variant in case of error. More...

virtual QVariant	minimumValue (int fieldIndex) const
	Returns the minimum value for an attribute column or an invalid variant in case of error. More...

virtual QgsCoordinateReferenceSystem	sourceCrs () const =0
	Returns the coordinate reference system for features in the source. More...

virtual QgsRectangle	sourceExtent () const
	Returns the extent of all geometries from the source. More...

virtual QString	sourceName () const =0
	Returns a friendly display name for the source. More...

virtual QSet< QVariant >	uniqueValues (int fieldIndex, int limit=-1) const
	Returns the set of unique values contained within the specified fieldIndex from this source. More...

virtual QgsWkbTypes::Type	wkbType () const =0
	Returns the geometry type for features returned by this source. More...

Detailed Description

An interface for objects which provide features via a getFeatures method.

Since: QGIS 3.0

Definition at line 37 of file qgsfeaturesource.h.

Member Enumeration Documentation

enum QgsFeatureSource::FeatureAvailability

Possible return value for hasFeatures() to determine if a source is empty.

It is implemented as a three-value logic, so it can return if there are features available for sure, if there are no features available for sure or if there might be features available but there is no guarantee for this.

Since: QGIS 3.4

Enumerator
NoFeaturesAvailable	There are certainly no features available in this source.
FeaturesAvailable	There is at least one feature available in this source.
FeaturesMaybeAvailable	There may be features available in this source.

Definition at line 50 of file qgsfeaturesource.h.

Constructor & Destructor Documentation

virtual QgsFeatureSource::~QgsFeatureSource ( )

virtualdefault

Member Function Documentation

QgsFeatureIds QgsFeatureSource::allFeatureIds ( ) const

virtual

Returns a list of all feature IDs for features present in the source.

Reimplemented in QgsProcessingFeatureSource.

Definition at line 115 of file qgsfeaturesource.cpp.

virtual long QgsFeatureSource::featureCount ( ) const

pure virtual

Returns the number of features contained in the source, or -1 if the feature count is unknown.

Implemented in QgsVectorLayer, QgsProcessingFeatureSource, QgsVectorLayerSelectedFeatureSource, and QgsVectorDataProvider.

virtual QgsFields QgsFeatureSource::fields ( ) const

pure virtual

Returns the fields associated with features in the source.

Implemented in QgsVectorLayer, QgsProcessingFeatureSource, QgsVectorLayerSelectedFeatureSource, and QgsVectorDataProvider.

virtual QgsFeatureIterator QgsFeatureSource::getFeatures ( const QgsFeatureRequest & request = QgsFeatureRequest() ) const

pure virtual

Returns an iterator for the features in the source.

An optional request can be used to optimise the returned iterator, eg by restricting the returned attributes or geometry.

Implemented in QgsVectorLayer, QgsProcessingFeatureSource, QgsVectorLayerSelectedFeatureSource, and QgsVectorDataProvider.

QgsFeatureSource::FeatureAvailability QgsFeatureSource::hasFeatures ( ) const

virtual

Determines if there are any features available in the source.

Since: QGIS 3.2

Reimplemented in QgsVectorLayer, QgsProcessingFeatureSource, and QgsVectorDataProvider.

Definition at line 26 of file qgsfeaturesource.cpp.

QgsVectorLayer * QgsFeatureSource::materialize	(	const QgsFeatureRequest &	request,
		QgsFeedback *	feedback = `nullptr`
	)

Materializes a request (query) made against this feature source, by running it over the source and returning a new memory based vector layer containing the result.

All settings from feature request will be honored.

If a subset of attributes has been set for the request, then only those selected fields will be present in the output layer.

The CRS for the output layer will match the input layer, unless QgsFeatureRequest::setDestinationCrs() has been called with a valid QgsCoordinateReferenceSystem. In this case the output layer will match the QgsFeatureRequest::destinationCrs() CRS.

The returned layer WKB type will match wkbType(), unless the QgsFeatureRequest::NoGeometry flag is set on the request. In that case the returned layer will not be a spatial layer.

An optional feedback argument can be used to cancel the materialization before it has fully completed.

The returned value is a new instance and the caller takes responsibility for its ownership.

Since: QGIS 3.0

Definition at line 132 of file qgsfeaturesource.cpp.

QVariant QgsFeatureSource::maximumValue ( int fieldIndex ) const

virtual

Returns the maximum value for an attribute column or an invalid variant in case of error.

The base class implementation uses a non-optimised approach of looping through all features in the source.

See also: minimumValue(); uniqueValues()

Reimplemented in QgsVectorLayer, QgsProcessingFeatureSource, and QgsVectorDataProvider.

Definition at line 75 of file qgsfeaturesource.cpp.

QVariant QgsFeatureSource::minimumValue ( int fieldIndex ) const

virtual

Returns the minimum value for an attribute column or an invalid variant in case of error.

The base class implementation uses a non-optimised approach of looping through all features in the source.

See also: maximumValue(); uniqueValues()

Reimplemented in QgsVectorLayer, QgsProcessingFeatureSource, and QgsVectorDataProvider.

Definition at line 52 of file qgsfeaturesource.cpp.

virtual QgsCoordinateReferenceSystem QgsFeatureSource::sourceCrs ( ) const

pure virtual

Returns the coordinate reference system for features in the source.

Implemented in QgsVectorLayer, QgsProcessingFeatureSource, QgsVectorLayerSelectedFeatureSource, and QgsVectorDataProvider.

QgsRectangle QgsFeatureSource::sourceExtent ( ) const

virtual

Returns the extent of all geometries from the source.

The base class implementation uses a non-optimised approach of looping through all features in the source.

Reimplemented in QgsVectorLayer, QgsProcessingFeatureSource, and QgsVectorDataProvider.

Definition at line 98 of file qgsfeaturesource.cpp.

virtual QString QgsFeatureSource::sourceName ( ) const

pure virtual

Returns a friendly display name for the source.

The returned value can be an empty string.

Implemented in QgsVectorLayer, QgsProcessingFeatureSource, QgsVectorLayerSelectedFeatureSource, and QgsVectorDataProvider.

QSet< QVariant > QgsFeatureSource::uniqueValues	(	int	fieldIndex,
		int	limit = `-1`
	)		const

virtual

Returns the set of unique values contained within the specified fieldIndex from this source.

If specified, the limit option can be used to limit the number of returned values. The base class implementation uses a non-optimised approach of looping through all features in the source.

See also: minimumValue(); maximumValue()

Reimplemented in QgsVectorLayer, and QgsProcessingFeatureSource.

Definition at line 31 of file qgsfeaturesource.cpp.

virtual QgsWkbTypes::Type QgsFeatureSource::wkbType ( ) const

pure virtual

Returns the geometry type for features returned by this source.

Implemented in QgsVectorLayer, QgsProcessingFeatureSource, QgsVectorLayerSelectedFeatureSource, and QgsVectorDataProvider.

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

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

Public Types

Public Member Functions

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation