QgsFeatureRequest Class Reference

This class wraps a request for features to a vector layer (or directly its vector data provider). More...

#include <qgsfeaturerequest.h>

Collaboration diagram for QgsFeatureRequest:

Public Types
enum	Flag { NoFlags = 0, NoGeometry = 1, SubsetOfAttributes = 2, ExactIntersect = 4 }
enum	FilterType { FilterNone, FilterRect, FilterFid }

Public Member Functions
	QgsFeatureRequest ()
	construct a default request: for all features get attributes and geometries More...
	QgsFeatureRequest (QgsFeatureId fid)
	construct a request with feature ID filter More...
	QgsFeatureRequest (const QgsRectangle &rect)
	construct a request with rectangle filter More...
	QgsFeatureRequest (const QgsFeatureRequest &rh)
	copy constructor More...
FilterType	filterType () const
QgsFeatureRequest &	setFilterRect (const QgsRectangle &rect)
	Set rectangle from which features will be taken. More...
const QgsRectangle &	filterRect () const
QgsFeatureRequest &	setFilterFid (QgsFeatureId fid)
	Set feature ID that should be fetched. More...
const QgsFeatureId &	filterFid () const
QgsFeatureRequest &	setFlags (Flags flags)
	Set flags that affect how features will be fetched. More...
const Flags &	flags () const
QgsFeatureRequest &	setSubsetOfAttributes (const QgsAttributeList &attrs)
	Set a subset of attributes that will be fetched. More...
const QgsAttributeList &	subsetOfAttributes () const
QgsFeatureRequest &	setSubsetOfAttributes (const QStringList &attrNames, const QgsFields &fields)
	Set a subset of attributes by names that will be fetched. More...

Protected Attributes
FilterType	mFilter
QgsRectangle	mFilterRect
QgsFeatureId	mFilterFid
Flags	mFlags
QgsAttributeList	mAttrs

Detailed Description

This class wraps a request for features to a vector layer (or directly its vector data provider).

The request may apply a filter to fetch only a particular subset of features. Currently supported filters:

• no filter - all features are returned
• feature id - only feature that matches given feature id is returned
• rectangle - only features that intersect given rectangle should be fetched. For the sake of speed, the intersection is often done only using feature's bounding box. There is a flag ExactIntersect that makes sure that only intersecting features will be returned.

For efficiency, it is also possible to tell provider that some data is not required:

• NoGeometry flag
• SubsetOfAttributes flag

The options may be chained, e.g.: QgsFeatureRequest().setFilterRect(QgsRectangle(0,0,1,1)).setFlags(QgsFeatureRequest::ExactIntersect)

Examples:

• fetch all features: QgsFeatureRequest()
• fetch all features, only one attribute QgsFeatureRequest().setSubsetOfAttributes(QStringList("myfield"), provider->fieldMap())
• fetch all features, without geometries QgsFeatureRequest().setFlags(QgsFeatureRequest::NoGeometry)
• fetch only features from particular extent QgsFeatureRequest().setFilterRect(QgsRectangle(0,0,1,1))
• fetch only one feature QgsFeatureRequest().setFilterFid(45)

Definition at line 55 of file qgsfeaturerequest.h.

Member Enumeration Documentation

enum QgsFeatureRequest::FilterType

Enumerator
FilterNone	No filter is applied.
FilterRect	Filter using a rectangle.
FilterFid	Filter using feature ID.

Definition at line 67 of file qgsfeaturerequest.h.

enum QgsFeatureRequest::Flag

Enumerator
NoFlags
NoGeometry	Do not fetch geometry.
SubsetOfAttributes	Fetch only a subset of attributes (setSubsetOfAttributes sets this flag)
ExactIntersect	Use exact geometry intersection (slower) instead of bounding boxes.

Definition at line 58 of file qgsfeaturerequest.h.

Constructor & Destructor Documentation

QgsFeatureRequest::QgsFeatureRequest

(

)

construct a default request: for all features get attributes and geometries

Definition at line 21 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest ( QgsFeatureId  fid )

explicit

construct a request with feature ID filter

Definition at line 27 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest ( const QgsRectangle &  rect )

explicit

construct a request with rectangle filter

Definition at line 34 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest

(

const QgsFeatureRequest &

rh

)

copy constructor

Definition at line 41 of file qgsfeaturerequest.cpp.

References mAttrs, mFilter, mFilterFid, mFilterRect, and mFlags.

Member Function Documentation

const QgsFeatureId& QgsFeatureRequest::filterFid ( ) const

inline

Definition at line 92 of file qgsfeaturerequest.h.

Referenced by QgsCacheIndexFeatureId::getCacheIterator(), and QgsVectorLayerFeatureIterator::nextFeatureFid().

const QgsRectangle& QgsFeatureRequest::filterRect ( ) const

inline

Definition at line 88 of file qgsfeaturerequest.h.

Referenced by QgsVectorLayerFeatureIterator::fetchNextAddedFeature(), and QgsVectorLayerFeatureIterator::fetchNextChangedGeomFeature().

FilterType QgsFeatureRequest::filterType ( ) const

inline

Definition at line 83 of file qgsfeaturerequest.h.

Referenced by QgsVectorLayerFeatureIterator::fetchNextAddedFeature(), QgsCacheIndexFeatureId::getCacheIterator(), QgsVectorLayerFeatureIterator::nextFeature(), QgsVectorLayerFeatureIterator::QgsVectorLayerFeatureIterator(), and QgsVectorLayerFeatureIterator::rewind().

const Flags& QgsFeatureRequest::flags ( ) const

inline

Definition at line 96 of file qgsfeaturerequest.h.

Referenced by QgsVectorLayerCache::checkInformationCovered(), QgsVectorLayerCache::getFeatures(), QgsVectorLayerFeatureIterator::nextFeature(), QgsVectorLayerFeatureIterator::nextFeatureFid(), QgsVectorLayerFeatureIterator::prepareJoins(), QgsVectorLayerFeatureIterator::QgsVectorLayerFeatureIterator(), setFlags(), QgsVectorLayerFeatureIterator::useAddedFeature(), and QgsVectorLayerFeatureIterator::useChangedAttributeFeature().

QgsFeatureRequest & QgsFeatureRequest::setFilterFid

(

QgsFeatureId

fid

)

Set feature ID that should be fetched.

Definition at line 58 of file qgsfeaturerequest.cpp.

References FilterFid, mFilter, and mFilterFid.

Referenced by QgsVectorLayer::selectedFeatures(), QgsVectorLayerUndoCommandChangeAttribute::undo(), QgsVectorLayer::updateFeature(), and QgsVectorLayerFeatureIterator::useChangedAttributeFeature().

QgsFeatureRequest & QgsFeatureRequest::setFilterRect

(

const QgsRectangle &

rect

)

Set rectangle from which features will be taken.

Empty rectangle removes the filter.

Definition at line 51 of file qgsfeaturerequest.cpp.

References FilterRect, mFilter, and mFilterRect.

Referenced by QgsComposerAttributeTable::getFeatureAttributes().

QgsFeatureRequest & QgsFeatureRequest::setFlags

(

Flags

flags

)

Set flags that affect how features will be fetched.

Definition at line 65 of file qgsfeaturerequest.cpp.

References flags(), and mFlags.

Referenced by QgsVectorLayerFeatureIterator::FetchJoinInfo::addJoinedAttributesDirect(), QgsComposerAttributeTable::getFeatureAttributes(), QgsVectorLayerCache::getFeatures(), QgsVectorLayerImport::importLayer(), QgsAttributeTableModel::QgsAttributeTableModel(), QgsVectorLayer::selectedFeatures(), QgsVectorLayerUndoCommandChangeAttribute::undo(), QgsVectorLayer::updateFeature(), QgsVectorLayerFeatureIterator::useChangedAttributeFeature(), and QgsVectorFileWriter::writeAsVectorFormat().

QgsFeatureRequest & QgsFeatureRequest::setSubsetOfAttributes

(

const QgsAttributeList &

attrs

)

Set a subset of attributes that will be fetched.

Empty list means that all attributes are used. To disable fetching attributes, reset the FetchAttributes flag (which is set by default)

Definition at line 71 of file qgsfeaturerequest.cpp.

References mAttrs, mFlags, and SubsetOfAttributes.

Referenced by QgsVectorLayerFeatureIterator::FetchJoinInfo::addJoinedAttributesDirect(), QgsZonalStatistics::calculateStatistics(), QgsGeometryAnalyzer::eventLayer(), QgsComposerAttributeTable::getFeatureAttributes(), QgsVectorLayerCache::getFeatures(), QgsVectorLayerImport::importLayer(), QgsVectorLayerFeatureIterator::prepareJoins(), QgsVectorLayerFeatureIterator::QgsVectorLayerFeatureIterator(), QgsVectorLayerUndoCommandChangeAttribute::undo(), QgsVectorLayer::updateFeature(), QgsVectorLayerFeatureIterator::useChangedAttributeFeature(), and QgsVectorFileWriter::writeAsVectorFormat().

QgsFeatureRequest & QgsFeatureRequest::setSubsetOfAttributes	(	const QStringList &	attrNames,
		const QgsFields &	fields
	)

Set a subset of attributes by names that will be fetched.

Definition at line 79 of file qgsfeaturerequest.cpp.

References QgsFields::count(), mAttrs, mFlags, and SubsetOfAttributes.

const QgsAttributeList& QgsFeatureRequest::subsetOfAttributes ( ) const

inline

Definition at line 101 of file qgsfeaturerequest.h.

Referenced by QgsVectorLayerCache::checkInformationCovered(), QgsVectorLayerCache::getFeatures(), QgsVectorLayerFeatureIterator::prepareJoins(), QgsVectorLayerFeatureIterator::QgsVectorLayerFeatureIterator(), and QgsVectorLayerFeatureIterator::useChangedAttributeFeature().

Member Data Documentation

QgsAttributeList QgsFeatureRequest::mAttrs

protected

Definition at line 116 of file qgsfeaturerequest.h.

Referenced by QgsFeatureRequest(), and setSubsetOfAttributes().

FilterType QgsFeatureRequest::mFilter

protected

Definition at line 112 of file qgsfeaturerequest.h.

Referenced by QgsFeatureRequest(), setFilterFid(), and setFilterRect().

QgsFeatureId QgsFeatureRequest::mFilterFid

protected

Definition at line 114 of file qgsfeaturerequest.h.

Referenced by QgsFeatureRequest(), and setFilterFid().

QgsRectangle QgsFeatureRequest::mFilterRect

protected

Definition at line 113 of file qgsfeaturerequest.h.

Referenced by QgsFeatureRequest(), and setFilterRect().

Flags QgsFeatureRequest::mFlags

protected

Definition at line 115 of file qgsfeaturerequest.h.

Referenced by QgsFeatureRequest(), setFlags(), and setSubsetOfAttributes().

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

• /build/buildd/qgis-2.0.1/src/core/qgsfeaturerequest.h
• /build/buildd/qgis-2.0.1/src/core/qgsfeaturerequest.cpp