For non-point geometry subclasses (points are always valid!) we
now cache the results of a geometry validity check. Subsequent
checks utilise the cached result wherever possible.
Because QgsGeometry/QgsFeature objects are implicitly shared, this
means that we avoid a *lot* of duplicate validity checks as
features and geometries are thrown around during processing model
execution.
Iterates over the geometries in the collection, allowing this type
of code:
gc = QgsGeometryCollection()
gc.fromWkt('GeometryCollection( Point(1 2), Point(11 12), LineString(33 34, 44 45))')
for part in gc:
print(part.asWkt())
- Calling removeGeometry with an invalid index will now raise an IndexError
- Calling collection[0] will return the first geometry in the collection,
collection[1] the second, etc. And negative indices return from the end
of the collection, so collection[-1] returns the last geometry in the collection.
- Geometries can be deleted by calling `del collection[1]` (deletes the
second geometry from the collection). Also supports negative indices
to count from the end of the collection.
This allows easy iteration over all the parts of a geometry,
regardless of the geometry's type. E.g.
geometry = QgsGeometry.fromWkt( 'MultiPoint( 0 0, 1 1, 2 2)' )
for part in geometry.parts():
print(part.asWkt())
geometry = QgsGeometry.fromWkt( 'LineString( 0 0, 10 10 )' )
for part in geometry.parts():
print(part.asWkt())
There are two iterators available. QgsGeometry.parts() gives
a non-const iterator, allowing the parts to be modified in place:
geometry = QgsGeometry.fromWkt( 'MultiPoint( 0 0, 1 1, 2 2)' )
for part in geometry.parts():
part.transform(ct)
For a const iteration, calling .const_parts() gives a const
iterator, which cannot edit the parts but avoids a potentially expensive
QgsGeometry detach and clone
geometry = QgsGeometry.fromWkt( 'MultiPoint( 0 0, 1 1, 2 2)' )
for part in geometry.const_parts():
print(part.x())
