Class: QgsCachedFeatureWriterIterator¶
- class qgis.core.QgsCachedFeatureWriterIterator(vlCache: QgsVectorLayerCache, featureRequest: QgsFeatureRequest)¶
Bases:
QgsAbstractFeatureIterator
This constructor creates a feature iterator, which queries the backend and caches retrieved features.
- Parameters
vlCache – The vector layer cache to use
featureRequest – The feature request to answer
QgsCachedFeatureWriterIterator(
QgsCachedFeatureWriterIterator
)Uses another iterator as backend and writes features to the cache
Methods
Close this iterator.
Remove reference, delete if refs == 0
Implementation for fetching a feature.
Returns a rectangle representing the original request’s
QgsFeatureRequest.filterRect()
.Transforms
feature
’s geometry according to the specified coordinatetransform
.By default, the iterator will fetch all features and check if the feature matches the expression.
By default, the iterator will fetch all features and check if the id is in the request.
Setup the simplification of geometries to fetch using the specified simplify method
Add reference
Rewind to the beginning of the iterator
- close(self) → bool¶
Close this iterator. No further features will be available.
- Return type
bool
- Returns
True
if successful
- deref(self)¶
Remove reference, delete if refs == 0
- fetchFeature(self, f: QgsFeature) → bool¶
Implementation for fetching a feature.
- Parameters
f (QgsFeature) – Will write to this feature
- Return type
bool
- Returns
bool
True
if the operation was OK
See also
bool()
- filterRectToSourceCrs(self, transform: QgsCoordinateTransform) → QgsRectangle¶
Returns a rectangle representing the original request’s
QgsFeatureRequest.filterRect()
. Iftransform
is a valid coordinate transform, the return rectangle will represent the requestedfilterRect()
transformed to the source’s coordinate reference system. Iterators should call this method and use the returned rectangle for filtering features to ensure that anyQgsFeatureRequest.destinationCrs()
set on the request is respected. Will throw aQgsCsException
if the rect cannot be transformed from the destination CRS.New in version 3.0.
- geometryToDestinationCrs(self, feature: QgsFeature, transform: QgsCoordinateTransform)¶
Transforms
feature
’s geometry according to the specified coordinatetransform
. Iffeature
has no geometry ortransform
is invalid then calling this method has no effect and will be shortcut. Iterators should call this method before returning features to ensure that anyQgsFeatureRequest.destinationCrs()
set on the request is respected.New in version 3.0.
- nextFeatureFilterExpression(self, f: QgsFeature) → bool¶
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
- nextFeatureFilterFids(self, f: QgsFeature) → bool¶
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
- prepareSimplification(self, simplifyMethod: QgsSimplifyMethod) → bool¶
Setup the simplification of geometries to fetch using the specified simplify method
- ref(self)¶
Add reference
- rewind(self) → bool¶
Rewind to the beginning of the iterator
- Return type
bool
- Returns
bool
True
if the operation was OK