Add some useful methods to resize QgsFeature attributes without clear…

…ing existing attributes
qgis · Dec 14, 2020 · 53831c6 · 53831c6
1 parent 55e6903
commit 53831c6
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Showing 5 changed files with 123 additions and 15 deletions.
diff --git a/python/core/auto_generated/qgsfeature.sip.in b/python/core/auto_generated/qgsfeature.sip.in
@@ -192,6 +192,13 @@ Returns the feature's attributes.
    Alternatively in Python: iterate feature, eg. @code [attr for attr in feature] @endcode
 
 .. versionadded:: 2.9
+%End
+
+    int attributeCount() const;
+%Docstring
+Returns the number of attributes attached to the feature.
+
+.. versionadded:: 3.18
 %End
 
     void setAttributes( const QgsAttributes &attrs );
@@ -252,6 +259,34 @@ The feature will be valid if it was successful.
 Initialize this feature with the given number of fields. Discard any previously set attribute data.
 
 :param fieldCount: Number of fields to initialize
+
+.. seealso:: :py:func:`resizedAttributes`
+%End
+
+    void resizeAttributes( int fieldCount );
+%Docstring
+Resizes the attributes attached to this feature to the given number of fields.
+
+If the new ``fieldCount`` is greater than the original number of fields then the additional attributes will
+be filled with NULL values. All existing attributes will remain unchanged.
+
+If the new ``fieldCount`` is less than the original number of fields then the unwanted values will be discarded from the
+end of the existing attributes.
+
+.. seealso:: :py:func:`initAttributes`
+
+.. seealso:: :py:func:`padAttributes`
+
+.. versionadded:: 3.18
+%End
+
+    void padAttributes( int count );
+%Docstring
+Resizes the attributes attached to this feature by appending the specified ``count`` of NULL values to the end of the existing attributes.
+
+.. seealso:: :py:func:`resizeAttributes`
+
+.. versionadded:: 3.18
 %End
 
     void deleteAttribute( int field );

diff --git a/src/analysis/processing/qgsalgorithmbatchgeocode.cpp b/src/analysis/processing/qgsalgorithmbatchgeocode.cpp
@@ -121,15 +121,10 @@ QgsFeatureList QgsBatchGeocodeAlgorithm::processFeature( const QgsFeature &featu
 {
   QgsFeature f = feature;
 
-  QgsAttributes attr = f.attributes();
-
   const QString address = f.attribute( mAddressField ).toString();
   if ( address.isEmpty() )
   {
-    // append null attributes
-    for ( int i = 0; i < mAdditionalFields.count(); ++ i )
-      attr.append( QVariant() );
-    f.setAttributes( attr );
+    f.padAttributes( mAdditionalFields.count() );
     feedback->pushWarning( QObject::tr( "Empty address field for feature %1" ).arg( feature.id() ) );
     return QgsFeatureList() << f;
   }
@@ -138,25 +133,19 @@ QgsFeatureList QgsBatchGeocodeAlgorithm::processFeature( const QgsFeature &featu
   const QList< QgsGeocoderResult > results = mGeocoder->geocodeString( address, geocodeContext, feedback );
   if ( results.empty() )
   {
-    // append null attributes
-    for ( int i = 0; i < mAdditionalFields.count(); ++ i )
-      attr.append( QVariant() );
-    f.setAttributes( attr );
+    f.padAttributes( mAdditionalFields.count() );
     feedback->pushWarning( QObject::tr( "No result for %1" ).arg( address ) );
     return QgsFeatureList() << f;
   }
 
   if ( !results.at( 0 ).isValid() )
   {
-    // append null attributes
-    for ( int i = 0; i < mAdditionalFields.count(); ++ i )
-      attr.append( QVariant() );
-    f.setAttributes( attr );
-
+    f.padAttributes( mAdditionalFields.count() );
     feedback->reportError( QObject::tr( "Error geocoding %1: %2" ).arg( address, results.at( 0 ).error() ) );
     return QgsFeatureList() << f;
   }
 
+  QgsAttributes attr = f.attributes();
   const QVariantMap additionalAttributes = results.at( 0 ).additionalAttributes();
   if ( !mIsInPlace )
   {

diff --git a/src/core/qgsfeature.cpp b/src/core/qgsfeature.cpp
@@ -126,6 +126,11 @@ QgsAttributes QgsFeature::attributes() const
   return d->attributes;
 }
 
+int QgsFeature::attributeCount() const
+{
+  return d->attributes.size();
+}
+
 void QgsFeature::setAttributes( const QgsAttributes &attrs )
 {
   if ( attrs == d->attributes )
@@ -210,6 +215,24 @@ void QgsFeature::initAttributes( int fieldCount )
   d->attributes.resize( fieldCount );
 }
 
+void QgsFeature::resizeAttributes( int fieldCount )
+{
+  if ( fieldCount == d->attributes.size() )
+    return;
+
+  d.detach();
+  d->attributes.resize( fieldCount );
+}
+
+void QgsFeature::padAttributes( int count )
+{
+  if ( count == 0 )
+    return;
+
+  d.detach();
+  d->attributes.resize( d->attributes.size() + count );
+}
+
 bool QgsFeature::setAttribute( int idx, const QVariant &value )
 {
   if ( idx < 0 || idx >= d->attributes.size() )

diff --git a/src/core/qgsfeature.h b/src/core/qgsfeature.h
@@ -237,6 +237,12 @@ class CORE_EXPORT QgsFeature
      */
     QgsAttributes attributes() const;
 
+    /**
+     * Returns the number of attributes attached to the feature.
+     * \since QGIS 3.18
+     */
+    int attributeCount() const;
+
     /**
      * Sets the feature's attributes.
      * The feature will be valid after.
@@ -285,9 +291,34 @@ class CORE_EXPORT QgsFeature
     /**
      * Initialize this feature with the given number of fields. Discard any previously set attribute data.
      * \param fieldCount Number of fields to initialize
+     *
+     * \see resizedAttributes()
      */
     void initAttributes( int fieldCount );
 
+    /**
+     * Resizes the attributes attached to this feature to the given number of fields.
+     *
+     * If the new \a fieldCount is greater than the original number of fields then the additional attributes will
+     * be filled with NULL values. All existing attributes will remain unchanged.
+     *
+     * If the new \a fieldCount is less than the original number of fields then the unwanted values will be discarded from the
+     * end of the existing attributes.
+     *
+     * \see initAttributes()
+     * \see padAttributes()
+     * \since QGIS 3.18
+     */
+    void resizeAttributes( int fieldCount );
+
+    /**
+     * Resizes the attributes attached to this feature by appending the specified \a count of NULL values to the end of the existing attributes.
+     *
+     * \see resizeAttributes()
+     * \since QGIS 3.18
+     */
+    void padAttributes( int count );
+
     /**
      * Deletes an attribute and its value.
      * \param field the index of the field

diff --git a/tests/src/python/test_qgsfeature.py b/tests/src/python/test_qgsfeature.py
@@ -165,6 +165,36 @@ def test_SetGeometry(self):
         feat.setGeometry(QgsPoint(12, 34))
         self.assertEqual(feat.geometry().asWkt(), 'Point (12 34)')
 
+    def testAttributeCount(self):
+        f = QgsFeature()
+        self.assertEqual(f.attributeCount(), 0)
+        f.setAttributes([1, 2, 3])
+        self.assertEqual(f.attributeCount(), 3)
+
+    def testResizeAttributes(self):
+        f = QgsFeature()
+        f.resizeAttributes(3)
+        self.assertEqual(f.attributes(), [NULL, NULL, NULL])
+        f.setAttributes([1, 2, 3])
+        f.resizeAttributes(3)
+        self.assertEqual(f.attributes(), [1, 2, 3])
+        f.resizeAttributes(5)
+        self.assertEqual(f.attributes(), [1, 2, 3, NULL, NULL])
+        f.resizeAttributes(2)
+        self.assertEqual(f.attributes(), [1, 2])
+
+    def testPadAttributes(self):
+        f = QgsFeature()
+        f.padAttributes(3)
+        self.assertEqual(f.attributes(), [NULL, NULL, NULL])
+        f.setAttributes([1, 2, 3])
+        f.padAttributes(0)
+        self.assertEqual(f.attributes(), [1, 2, 3])
+        f.padAttributes(2)
+        self.assertEqual(f.attributes(), [1, 2, 3, NULL, NULL])
+        f.padAttributes(3)
+        self.assertEqual(f.attributes(), [1, 2, 3, NULL, NULL, NULL, NULL, NULL])
+
 
 if __name__ == '__main__':
     unittest.main()