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

Collaboration diagram for QgsFeatureRequest:

Public Types
enum	FilterType { FilterNone, FilterRect, FilterFid }
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 QgsFeatureRequest &rh)
	copy constructor
const QgsFeatureId &	filterFid () const
const QgsRectangle &	filterRect () const
FilterType	filterType () const
const Flags &	flags () const
QgsFeatureRequest &	setFilterFid (QgsFeatureId fid)
	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 &	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 QgsAttributeList &	subsetOfAttributes () const
Protected Attributes
QgsAttributeList	mAttrs
FilterType	mFilter
QgsFeatureId	mFilterFid
QgsRectangle	mFilterRect
Flags	mFlags

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:

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

Enumerator:

Definition at line 67 of file qgsfeaturerequest.h.

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.