Internal feature iterator to be implemented within data providers. More...

#include <qgsfeatureiterator.h>

Inheritance diagram for QgsAbstractFeatureIterator:

[legend]

Public Types
enum	CompileStatus { NoCompilation, PartiallyCompiled, Compiled }
	Status of expression compilation for filter expression requests. More...

Public Member Functions
	QgsAbstractFeatureIterator (const QgsFeatureRequest &request)
	base class constructor - stores the iteration parameters More...

virtual	~QgsAbstractFeatureIterator ()
	destructor makes sure that the iterator is closed properly More...

virtual bool	close ()=0
	end of iterating: free the resources / lock More...

CompileStatus	compileStatus () const
	Returns the status of expression compilation for filter expression requests. More...

virtual bool	nextFeature (QgsFeature &f)
	fetch next feature, return true on success More...

virtual bool	rewind ()=0
	reset the iterator to the starting position More...

virtual void	setInterruptionChecker (QgsInterruptionChecker *interruptionChecker)
	Attach an object that can be queried regularly by the iterator to check if it must stopped. More...

Protected Member Functions
void	deref ()
	remove reference, delete if refs == 0 More...

virtual bool	fetchFeature (QgsFeature &f)=0
	If you write a feature iterator for your provider, this is the method you need to implement!! More...

virtual bool	nextFeatureFilterExpression (QgsFeature &f)
	By default, the iterator will fetch all features and check if the feature matches the expression. More...

virtual bool	nextFeatureFilterFids (QgsFeature &f)
	By default, the iterator will fetch all features and check if the id is in the request. More...

virtual bool	prepareSimplification (const QgsSimplifyMethod &simplifyMethod)
	Setup the simplification of geometries to fetch using the specified simplify method. More...

void	ref ()
	add reference More...

Protected Attributes
bool	mClosed
	Set to true, as soon as the iterator is closed. More...

CompileStatus	mCompileStatus
	Status of compilation of filter expression. More...

long	mFetchedCount
	Number of features already fetched by iterator. More...

QgsFeatureRequest	mRequest
	A copy of the feature request. More...

bool	mZombie
	A feature iterator may be closed already but still be serving features from the cache. More...

int	refs
	reference counting (to allow seamless copying of QgsFeatureIterator instances) TODO QGIS3: make this private More...

Friends
class	QgsFeatureIterator

Detailed Description

Internal feature iterator to be implemented within data providers.

Definition at line 39 of file qgsfeatureiterator.h.

Member Enumeration Documentation

◆ CompileStatus

enum QgsAbstractFeatureIterator::CompileStatus

Status of expression compilation for filter expression requests.

Enumerator
NoCompilation	Expression could not be compiled or not attempt was made to compile expression
PartiallyCompiled	Expression was partially compiled, but extra checks need to be applied to features
Compiled	Expression was fully compiled and delegated to data provider source

Definition at line 44 of file qgsfeatureiterator.h.

Constructor & Destructor Documentation

◆ QgsAbstractFeatureIterator()

QgsAbstractFeatureIterator::QgsAbstractFeatureIterator ( const QgsFeatureRequest & request )

base class constructor - stores the iteration parameters

Definition at line 22 of file qgsfeatureiterator.cpp.

◆ ~QgsAbstractFeatureIterator()

QgsAbstractFeatureIterator::~QgsAbstractFeatureIterator ( )

virtual

destructor makes sure that the iterator is closed properly

Definition at line 33 of file qgsfeatureiterator.cpp.

Member Function Documentation

◆ close()

virtual bool QgsAbstractFeatureIterator::close ( )

pure virtual

end of iterating: free the resources / lock

Implemented in QgsCachedFeatureWriterIterator, QgsVectorLayerFeatureIterator, and QgsCachedFeatureIterator.

◆ compileStatus()

CompileStatus QgsAbstractFeatureIterator::compileStatus ( ) const

inline

Returns the status of expression compilation for filter expression requests.

Note: added in QGIS 2.16

Definition at line 78 of file qgsfeatureiterator.h.

◆ deref()

void QgsAbstractFeatureIterator::deref ( )

protected

remove reference, delete if refs == 0

Definition at line 122 of file qgsfeatureiterator.cpp.

◆ fetchFeature()

virtual bool QgsAbstractFeatureIterator::fetchFeature ( QgsFeature & f )

protectedpure virtual

If you write a feature iterator for your provider, this is the method you need to implement!!

Parameters

f	The feature to write to

Returns: true if a feature was written to f

Implemented in QgsCachedFeatureWriterIterator, QgsVectorLayerFeatureIterator, and QgsCachedFeatureIterator.

◆ nextFeature()

bool QgsAbstractFeatureIterator::nextFeature ( QgsFeature & f )

virtual

fetch next feature, return true on success

Definition at line 37 of file qgsfeatureiterator.cpp.

◆ nextFeatureFilterExpression()

bool QgsAbstractFeatureIterator::nextFeatureFilterExpression ( QgsFeature & f )

protectedvirtual

By default, the iterator will fetch all features and check if the feature matches the expression.

If you have a more sophisticated metodology (SQL request for the features...) and you check for the expression in your fetchFeature method, you can just redirect this call to fetchFeature so the default check will be omitted.

Parameters

f	The feature to write to

Returns: true if a feature was written to f

Reimplemented in QgsVectorLayerFeatureIterator.

Definition at line 84 of file qgsfeatureiterator.cpp.

◆ nextFeatureFilterFids()

bool QgsAbstractFeatureIterator::nextFeatureFilterFids ( QgsFeature & f )

protectedvirtual

By default, the iterator will fetch all features and check if the id is in the request.

If you have a more sophisticated metodology (SQL request for the features...) and you are sure, that any feature you return from fetchFeature will match if the request was FilterFids you can just redirect this call to fetchFeature so the default check will be omitted.

Parameters

f	The feature to write to

Returns: true if a feature was written to f

Reimplemented in QgsCachedFeatureIterator.

Definition at line 95 of file qgsfeatureiterator.cpp.

◆ prepareSimplification()

bool QgsAbstractFeatureIterator::prepareSimplification ( const QgsSimplifyMethod & simplifyMethod )

protectedvirtual

Setup the simplification of geometries to fetch using the specified simplify method.

Reimplemented in QgsVectorLayerFeatureIterator.

Definition at line 129 of file qgsfeatureiterator.cpp.

◆ ref()

void QgsAbstractFeatureIterator::ref ( )

protected

add reference

Definition at line 105 of file qgsfeatureiterator.cpp.

◆ rewind()

virtual bool QgsAbstractFeatureIterator::rewind ( )

pure virtual

reset the iterator to the starting position

Implemented in QgsCachedFeatureWriterIterator, QgsVectorLayerFeatureIterator, and QgsCachedFeatureIterator.

◆ setInterruptionChecker()

void QgsAbstractFeatureIterator::setInterruptionChecker ( QgsInterruptionChecker * interruptionChecker )

virtual

Attach an object that can be queried regularly by the iterator to check if it must stopped.

This is mostly useful for iterators where a single nextFeature()/fetchFeature() iteration might be very long. A typical use case is the WFS provider. When nextFeature()/fetchFeature() is reasonably fast, it is not necessary to implement this method. The default implementation does nothing.

Note: added in QGIS 2.16; not available in Python bindings

Reimplemented in QgsVectorLayerFeatureIterator.

Definition at line 193 of file qgsfeatureiterator.cpp.

Friends And Related Function Documentation

◆ QgsFeatureIterator

friend class QgsFeatureIterator

friend

Definition at line 135 of file qgsfeatureiterator.h.

Member Data Documentation

◆ mClosed

bool QgsAbstractFeatureIterator::mClosed

protected

Set to true, as soon as the iterator is closed.

Definition at line 119 of file qgsfeatureiterator.h.

◆ mCompileStatus

CompileStatus QgsAbstractFeatureIterator::mCompileStatus

protected

Status of compilation of filter expression.

Definition at line 141 of file qgsfeatureiterator.h.

◆ mFetchedCount

long QgsAbstractFeatureIterator::mFetchedCount

protected

Number of features already fetched by iterator.

Definition at line 138 of file qgsfeatureiterator.h.

◆ mRequest

QgsFeatureRequest QgsAbstractFeatureIterator::mRequest

protected

A copy of the feature request.

Definition at line 116 of file qgsfeatureiterator.h.

◆ mZombie

bool QgsAbstractFeatureIterator::mZombie

protected

A feature iterator may be closed already but still be serving features from the cache.

This is done when we serve features which have been pre-fetched and the order by has been locally sorted. In such a scenario, all resources have been released (mClosed is true) but the deads are still alive.

Definition at line 128 of file qgsfeatureiterator.h.

◆ refs

int QgsAbstractFeatureIterator::refs

protected

reference counting (to allow seamless copying of QgsFeatureIterator instances) TODO QGIS3: make this private

Definition at line 132 of file qgsfeatureiterator.h.

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

/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsfeatureiterator.h
/tmp/buildd/qgis-2.18.21+99unstable/src/core/qgsfeatureiterator.cpp

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Friends

Detailed Description

Member Enumeration Documentation

◆ CompileStatus

Constructor & Destructor Documentation

◆ QgsAbstractFeatureIterator()

◆ ~QgsAbstractFeatureIterator()

Member Function Documentation

◆ close()

◆ compileStatus()

◆ deref()

◆ fetchFeature()

◆ nextFeature()

◆ nextFeatureFilterExpression()

◆ nextFeatureFilterFids()

◆ prepareSimplification()

◆ ref()

◆ rewind()

◆ setInterruptionChecker()

Friends And Related Function Documentation

◆ QgsFeatureIterator

Member Data Documentation

◆ mClosed

◆ mCompileStatus

◆ mFetchedCount

◆ mRequest

◆ mZombie

◆ refs