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

#include <qgsfeaturerequest.h>

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

Public Member Functions
	QgsFeatureRequest ()
	construct a default request: for all features get attributes and geometries
	QgsFeatureRequest (QgsFeatureId fid)
	construct a request with feature ID filter
	QgsFeatureRequest (const QgsRectangle &rect)
	construct a request with rectangle filter
	QgsFeatureRequest (const QgsExpression &expr)
	construct a request with a filter expression
	QgsFeatureRequest (const QgsFeatureRequest &rh)
	copy constructor
	~QgsFeatureRequest ()
bool	acceptFeature (const QgsFeature &feature)
	Check if a feature is accepted by this requests filter.
QgsExpression *	filterExpression () const
const QgsFeatureId &	filterFid () const
const QgsFeatureIds &	filterFids () const
const QgsRectangle &	filterRect () const
FilterType	filterType () const
const Flags &	flags () const
QgsFeatureRequest &	operator= (const QgsFeatureRequest &rh)
QgsFeatureRequest &	setFilterExpression (const QString &expression)
	Set filter expression. {.
QgsFeatureRequest &	setFilterFid (QgsFeatureId fid)
	Set feature ID that should be fetched.
QgsFeatureRequest &	setFilterFids (QgsFeatureIds fids)
	Set feature ID that should be fetched.
QgsFeatureRequest &	setFilterRect (const QgsRectangle &rect)
	Set rectangle from which features will be taken.
QgsFeatureRequest &	setFlags (Flags flags)
	Set flags that affect how features will be fetched.
QgsFeatureRequest &	setSimplifyMethod (const QgsSimplifyMethod &simplifyMethod)
	Set a simplification method for geometries that will be fetched.
QgsFeatureRequest &	setSubsetOfAttributes (const QgsAttributeList &attrs)
	Set a subset of attributes that will be fetched.
QgsFeatureRequest &	setSubsetOfAttributes (const QStringList &attrNames, const QgsFields &fields)
	Set a subset of attributes by names that will be fetched.
const QgsSimplifyMethod &	simplifyMethod () const
	Get simplification method for geometries that will be fetched.
const QgsAttributeList &	subsetOfAttributes () const

Static Public Attributes
static const QString	AllAttributes = QString( "#!allattributes!#" )

Protected Attributes
QgsAttributeList	mAttrs
FilterType	mFilter
QgsExpression *	mFilterExpression
QgsFeatureId	mFilterFid
QgsFeatureIds	mFilterFids
QgsRectangle	mFilterRect
Flags	mFlags
QgsSimplifyMethod	mSimplifyMethod

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
SimplifyMethod for geometries to fetch

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 58 of file qgsfeaturerequest.h.

Member Enumeration Documentation

enum QgsFeatureRequest::FilterType

Enumerator:

FilterNone	No filter is applied.
FilterRect	Filter using a rectangle, no need to set NoGeometry.
FilterFid	Filter using feature ID.
FilterExpression	Filter using expression.
FilterFids	Filter using feature IDs.

Definition at line 70 of file qgsfeaturerequest.h.

enum QgsFeatureRequest::Flag

Enumerator:

NoFlags
NoGeometry	Geometry is not required. It may still be returned if e.g. required for a filter condition.
SubsetOfAttributes	Fetch only a subset of attributes (setSubsetOfAttributes sets this flag)
ExactIntersect	Use exact geometry intersection (slower) instead of bounding boxes.

Definition at line 61 of file qgsfeaturerequest.h.

Constructor & Destructor Documentation

QgsFeatureRequest::QgsFeatureRequest ( )

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

Definition at line 25 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest ( QgsFeatureId fid )

explicit

construct a request with feature ID filter

Definition at line 33 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest ( const QgsRectangle & rect )

explicit

construct a request with rectangle filter

Definition at line 41 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest ( const QgsExpression & expr )

explicit

construct a request with a filter expression

Definition at line 50 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::QgsFeatureRequest ( const QgsFeatureRequest & rh )

copy constructor

Definition at line 58 of file qgsfeaturerequest.cpp.

QgsFeatureRequest::~QgsFeatureRequest ( )

Definition at line 83 of file qgsfeaturerequest.cpp.

Member Function Documentation

bool QgsFeatureRequest::acceptFeature ( const QgsFeature & feature )

Check if a feature is accepted by this requests filter.

Parameters

feature The feature which will be tested

Returns: true, if the filter accepts the feature

Note: added in 2.1

Definition at line 157 of file qgsfeaturerequest.cpp.

QgsExpression* QgsFeatureRequest::filterExpression ( ) const

inline

Definition at line 113 of file qgsfeaturerequest.h.

const QgsFeatureId& QgsFeatureRequest::filterFid ( ) const

inline

Definition at line 105 of file qgsfeaturerequest.h.

const QgsFeatureIds& QgsFeatureRequest::filterFids ( ) const

inline

Definition at line 109 of file qgsfeaturerequest.h.

const QgsRectangle& QgsFeatureRequest::filterRect ( ) const

inline

Definition at line 101 of file qgsfeaturerequest.h.

FilterType QgsFeatureRequest::filterType ( ) const

inline

Definition at line 96 of file qgsfeaturerequest.h.

const Flags& QgsFeatureRequest::flags ( ) const

inline

Definition at line 117 of file qgsfeaturerequest.h.

QgsFeatureRequest & QgsFeatureRequest::operator= ( const QgsFeatureRequest & rh )

Definition at line 63 of file qgsfeaturerequest.cpp.

QgsFeatureRequest & QgsFeatureRequest::setFilterExpression ( const QString & expression )

Set filter expression. {.

See Also: QgsExpression}

Definition at line 109 of file qgsfeaturerequest.cpp.

QgsFeatureRequest & QgsFeatureRequest::setFilterFid ( QgsFeatureId fid )

Set feature ID that should be fetched.

Definition at line 95 of file qgsfeaturerequest.cpp.

QgsFeatureRequest & QgsFeatureRequest::setFilterFids ( QgsFeatureIds fids )

Set feature ID that should be fetched.

Definition at line 102 of file qgsfeaturerequest.cpp.

QgsFeatureRequest & QgsFeatureRequest::setFilterRect ( const QgsRectangle & rect )

Set rectangle from which features will be taken.

Empty rectangle removes the filter.

Definition at line 88 of file qgsfeaturerequest.cpp.

QgsFeatureRequest & QgsFeatureRequest::setFlags ( Flags flags )

Set flags that affect how features will be fetched.

Definition at line 117 of file qgsfeaturerequest.cpp.

QgsFeatureRequest & QgsFeatureRequest::setSimplifyMethod ( const QgsSimplifyMethod & simplifyMethod )

Set a simplification method for geometries that will be fetched.

Note: added in 2.2

Definition at line 151 of file qgsfeaturerequest.cpp.

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 123 of file qgsfeaturerequest.cpp.

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

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

Definition at line 130 of file qgsfeaturerequest.cpp.

const QgsSimplifyMethod& QgsFeatureRequest::simplifyMethod ( ) const

inline

Get simplification method for geometries that will be fetched.

Note: added in 2.2

Definition at line 132 of file qgsfeaturerequest.h.

const QgsAttributeList& QgsFeatureRequest::subsetOfAttributes ( ) const

inline

Definition at line 122 of file qgsfeaturerequest.h.

Member Data Documentation

const QString QgsFeatureRequest::AllAttributes = QString( "#!allattributes!#" )

static

Definition at line 79 of file qgsfeaturerequest.h.

QgsAttributeList QgsFeatureRequest::mAttrs

protected

Definition at line 156 of file qgsfeaturerequest.h.

FilterType QgsFeatureRequest::mFilter

protected

Definition at line 150 of file qgsfeaturerequest.h.

QgsExpression* QgsFeatureRequest::mFilterExpression

protected

Definition at line 154 of file qgsfeaturerequest.h.

QgsFeatureId QgsFeatureRequest::mFilterFid

protected

Definition at line 152 of file qgsfeaturerequest.h.

QgsFeatureIds QgsFeatureRequest::mFilterFids

protected

Definition at line 153 of file qgsfeaturerequest.h.

QgsRectangle QgsFeatureRequest::mFilterRect

protected

Definition at line 151 of file qgsfeaturerequest.h.

Flags QgsFeatureRequest::mFlags

protected

Definition at line 155 of file qgsfeaturerequest.h.

QgsSimplifyMethod QgsFeatureRequest::mSimplifyMethod

protected

Definition at line 157 of file qgsfeaturerequest.h.

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

/tmp/buildd/qgis-2.8.2+12wheezy/src/core/qgsfeaturerequest.h
/tmp/buildd/qgis-2.8.2+12wheezy/src/core/qgsfeaturerequest.cpp

Public Types

Public Member Functions

Static Public Attributes

Protected Attributes

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation