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Add a base class implemention for QgsVectorDataProvider::changeFeatures

Previously this method would only succeed for providers which
explicitly implement it. Now, providers which do not implement
changeFeatures but do support both ChangeAttributeValues
and ChangeGeometries capabilities will use a non-optimised
version of changeFeatures which calls changeAttributeValues
and changeGeometries in turn.

This makes QgsVectorDataProvider::changeFeatures easier to use
in scripts - instead of writing manual fallbacks for providers
which do not implement it you can instead safely call this
method regardless of the provider and it will succeed wherever
both the attributes/geometries can be changed.

Also add a provider unit test covering this.
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nyalldawson committed Dec 27, 2016
1 parent 901cd29 commit b256075e30b374ca0640ca2ed39e047c1affb4aa
Showing with 61 additions and 5 deletions.
  1. +7 −3 src/core/qgsvectordataprovider.cpp
  2. +6 −2 src/core/qgsvectordataprovider.h
  3. +48 −0 tests/src/python/providertestbase.py
@@ -128,9 +128,13 @@ bool QgsVectorDataProvider::changeGeometryValues( const QgsGeometryMap &geometry
bool QgsVectorDataProvider::changeFeatures( const QgsChangedAttributesMap &attr_map,
const QgsGeometryMap &geometry_map )
{
Q_UNUSED( attr_map );
Q_UNUSED( geometry_map );
return false;
if ( !( capabilities() & ChangeAttributeValues ) || !( capabilities() & ChangeGeometries ) )
return false;

bool result = true;
result = result && changeAttributeValues( attr_map );
result = result && changeGeometryValues( geometry_map );
return result;
}

bool QgsVectorDataProvider::createSpatialIndex()
@@ -274,14 +274,18 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider
virtual bool renameAttributes( const QgsFieldNameMap& renamedAttributes );

/**
* Changes attribute values of existing features.
* Changes attribute values of existing features. This should
* succeed if the provider reports the ChangeAttributeValues capability.
* @param attr_map a map containing changed attributes
* @return true in case of success and false in case of failure
*/
virtual bool changeAttributeValues( const QgsChangedAttributesMap &attr_map );

/**
* Changes attribute values and geometries of existing features.
* Changes attribute values and geometries of existing features. This should
* succeed if the provider reports both the ChangeAttributeValues and
* ChangeGeometries capabilities. Providers which report the ChangeFeatures
* capability implement an optimised version of this method.
* @param attr_map a map containing changed attributes
* @param geometry_map A QgsGeometryMap whose index contains the feature IDs
* that will have their geometries changed.
@@ -802,3 +802,51 @@ def testChangeGeometries(self):
# expect fail
self.assertFalse(l.dataProvider().changeGeometryValues(changes),
'Provider reported no ChangeGeometries capability, but returned true to changeGeometryValues')

def testChangeFeatures(self):
if not getattr(self, 'getEditableLayer', None):
return

l = self.getEditableLayer()
self.assertTrue(l.isValid())

features = [f for f in l.dataProvider().getFeatures()]

# find 2 features to change attributes for
features = [f for f in l.dataProvider().getFeatures()]
# need to keep order here
to_change = [f for f in features if f.attributes()[0] == 1]
to_change.extend([f for f in features if f.attributes()[0] == 2])
# changes by feature id, for changeAttributeValues call
attribute_changes = {to_change[0].id(): {1: 501, 3: 'new string'}, to_change[1].id(): {1: 502, 4: 'NEW'}}
# changes by pk, for testing after retrieving changed features
new_attr_map = {1: {1: 501, 3: 'new string'}, 2: {1: 502, 4: 'NEW'}}

# find 2 features to change geometries for
to_change = [f for f in features if f.attributes()[0] == 1]
to_change.extend([f for f in features if f.attributes()[0] == 3])
# changes by feature id, for changeGeometryValues call
geometry_changes = {to_change[0].id(): QgsGeometry.fromWkt('Point (10 20)'), to_change[1].id(): QgsGeometry()}
# changes by pk, for testing after retrieving changed features
new_geom_map = {1: QgsGeometry.fromWkt('Point ( 10 20 )'), 3: QgsGeometry()}

if l.dataProvider().capabilities() & QgsVectorDataProvider.ChangeGeometries and l.dataProvider().capabilities() & QgsVectorDataProvider.ChangeAttributeValues:
# expect success
result = l.dataProvider().changeFeatures(attribute_changes, geometry_changes)
self.assertTrue(result,
'Provider reported ChangeGeometries and ChangeAttributeValues capability, but returned False to changeFeatures')

# check result
self.testGetFeatures(l.dataProvider(), changed_attributes=new_attr_map, changed_geometries=new_geom_map)

# change empty list, should return true for consistency
self.assertTrue(l.dataProvider().changeFeatures({}, {}))

elif not l.dataProvider().capabilities() & QgsVectorDataProvider.ChangeGeometries:
# expect fail
self.assertFalse(l.dataProvider().changeFeatures(attribute_changes, geometry_changes),
'Provider reported no ChangeGeometries capability, but returned true to changeFeatures')
elif not l.dataProvider().capabilities() & QgsVectorDataProvider.ChangeAttributeValues:
# expect fail
self.assertFalse(l.dataProvider().changeFeatures(attribute_changes, geometry_changes),
'Provider reported no ChangeAttributeValues capability, but returned true to changeFeatures')

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