QgsFeatureRequest Class Reference

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

#include <qgsfeaturerequest.h>

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

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

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

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

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.

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.

Constructor & Destructor Documentation

QgsFeatureRequest::QgsFeatureRequest

(

)

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

QgsFeatureRequest::QgsFeatureRequest ( QgsFeatureId  fid )

explicit

construct a request with feature ID filter

QgsFeatureRequest::QgsFeatureRequest ( const QgsRectangle &  rect )

explicit

construct a request with rectangle filter

QgsFeatureRequest::QgsFeatureRequest ( const QgsExpression &  expr )

explicit

construct a request with a filter expression

QgsFeatureRequest::QgsFeatureRequest

(

const QgsFeatureRequest &

rh

)

copy constructor

QgsFeatureRequest::~QgsFeatureRequest

(

)

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

QgsExpression* QgsFeatureRequest::filterExpression ( ) const

inline

const QgsFeatureId& QgsFeatureRequest::filterFid ( ) const

inline

const QgsFeatureIds& QgsFeatureRequest::filterFids ( ) const

inline

const QgsRectangle& QgsFeatureRequest::filterRect ( ) const

inline

FilterType QgsFeatureRequest::filterType ( ) const

inline

const Flags& QgsFeatureRequest::flags ( ) const

inline

QgsFeatureRequest & QgsFeatureRequest::operator=

(

const QgsFeatureRequest &

rh

)

QgsFeatureRequest & QgsFeatureRequest::setFilterExpression

(

const QString &

expression

)

Set filter expression. {.

See Also

QgsExpression}

QgsFeatureRequest & QgsFeatureRequest::setFilterFid

(

QgsFeatureId

fid

)

Set feature ID that should be fetched.

QgsFeatureRequest & QgsFeatureRequest::setFilterFids

(

QgsFeatureIds

fids

)

Set feature ID that should be fetched.

QgsFeatureRequest & QgsFeatureRequest::setFilterRect

(

const QgsRectangle &

rect

)

Set rectangle from which features will be taken.

Empty rectangle removes the filter.

QgsFeatureRequest & QgsFeatureRequest::setFlags

(

Flags

flags

)

Set flags that affect how features will be fetched.

QgsFeatureRequest & QgsFeatureRequest::setSimplifyMethod

(

const QgsSimplifyMethod &

simplifyMethod

)

Set a simplification method for geometries that will be fetched.

Note

added in 2.2

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)

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

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

const QgsSimplifyMethod& QgsFeatureRequest::simplifyMethod ( ) const

inline

Get simplification method for geometries that will be fetched.

Note

added in 2.2

const QgsAttributeList& QgsFeatureRequest::subsetOfAttributes ( ) const

inline

Member Data Documentation

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

static

QgsAttributeList QgsFeatureRequest::mAttrs

protected

FilterType QgsFeatureRequest::mFilter

protected

QgsExpression* QgsFeatureRequest::mFilterExpression

protected

QgsFeatureId QgsFeatureRequest::mFilterFid

protected

QgsFeatureIds QgsFeatureRequest::mFilterFids

protected

QgsRectangle QgsFeatureRequest::mFilterRect

protected

Flags QgsFeatureRequest::mFlags

protected

QgsSimplifyMethod QgsFeatureRequest::mSimplifyMethod

protected

---

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

• /tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgsfeaturerequest.h
• /tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgsfeaturerequest.cpp