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

#include <qgsfeatureiterator.h>

Inheritance diagram for QgsAbstractFeatureIterator:

Collaboration diagram for QgsAbstractFeatureIterator:

Public Member Functions
	QgsAbstractFeatureIterator (const QgsFeatureRequest &request)
	base class constructor - stores the iteration parameters
virtual	~QgsAbstractFeatureIterator ()
	destructor makes sure that the iterator is closed properly
virtual bool	nextFeature (QgsFeature &f)
	fetch next feature, return true on success
virtual bool	rewind ()=0
	reset the iterator to the starting position
virtual bool	close ()=0
	end of iterating: free the resources / lock

Protected Member Functions
virtual bool	fetchFeature (QgsFeature &f)=0
	If you write a feature iterator for your provider, this is the method you need to implement!!
virtual bool	nextFeatureFilterExpression (QgsFeature &f)
	By default, the iterator will fetch all features and check if the feature matches the expression.
virtual bool	nextFeatureFilterFids (QgsFeature &f)
	By default, the iterator will fetch all features and check if the id is in the request.
void	ref ()
	add reference
void	deref ()
	remove reference, delete if refs == 0
virtual bool	prepareSimplification (const QgsSimplifyMethod &simplifyMethod)
	Setup the simplification of geometries to fetch using the specified simplify method.

Protected Attributes
QgsFeatureRequest	mRequest
	A copy of the feature request.
bool	mClosed
	Set to true, as soon as the iterator is closed.
int	refs
	reference counting (to allow seamless copying of QgsFeatureIterator instances)

Private Member Functions
virtual bool	providerCanSimplify (QgsSimplifyMethod::MethodType methodType) const
	returns whether the iterator supports simplify geometries on provider side
virtual bool	simplify (QgsFeature &feature)
	simplify the specified geometry if it was configured

Private Attributes
QgsAbstractGeometrySimplifier *	mGeometrySimplifier
	optional object to locally simplify geometries fetched by this feature iterator
bool	mLocalSimplification
	this iterator runs local simplification

Friends
class	QgsFeatureIterator

Detailed Description

Internal feature iterator to be implemented within data providers.

Definition at line 26 of file qgsfeatureiterator.h.

Constructor & Destructor Documentation

QgsAbstractFeatureIterator::QgsAbstractFeatureIterator ( const QgsFeatureRequest & request )

base class constructor - stores the iteration parameters

Definition at line 21 of file qgsfeatureiterator.cpp.

QgsAbstractFeatureIterator::~QgsAbstractFeatureIterator ( )

virtual

destructor makes sure that the iterator is closed properly

Definition at line 30 of file qgsfeatureiterator.cpp.

References mGeometrySimplifier.

Member Function Documentation

virtual bool QgsAbstractFeatureIterator::close ( )

pure virtual

end of iterating: free the resources / lock

Implemented in QgsCachedFeatureWriterIterator, QgsCachedFeatureIterator, and QgsVectorLayerFeatureIterator.

Referenced by QgsFeatureIterator::close().

void QgsAbstractFeatureIterator::deref ( )

protected

remove reference, delete if refs == 0

Definition at line 98 of file qgsfeatureiterator.cpp.

References refs.

Referenced by QgsFeatureIterator::operator=(), and QgsFeatureIterator::~QgsFeatureIterator().

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, QgsCachedFeatureIterator, and QgsVectorLayerFeatureIterator.

Referenced by nextFeature(), QgsVectorLayerFeatureIterator::nextFeatureFilterExpression(), nextFeatureFilterExpression(), nextFeatureFilterFids(), and QgsCachedFeatureIterator::nextFeatureFilterFids().

bool QgsAbstractFeatureIterator::nextFeature ( QgsFeature & f )

virtual

fetch next feature, return true on success

Definition at line 36 of file qgsfeatureiterator.cpp.

References fetchFeature(), QgsFeatureRequest::FilterExpression, QgsFeatureRequest::FilterFids, QgsFeatureRequest::filterType(), QgsFeature::geometry(), mLocalSimplification, mRequest, nextFeatureFilterExpression(), nextFeatureFilterFids(), and simplify().

Referenced by QgsFeatureIterator::nextFeature().

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 64 of file qgsfeatureiterator.cpp.

References QgsExpression::evaluate(), fetchFeature(), QgsFeatureRequest::filterExpression(), and mRequest.

Referenced by nextFeature().

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