New class QgsVectorLayerUtils

Contains static helper methods for working with vector layers. Initially only contains a method to test whether a value exists within a layer's attributes.
qgis · Nov 2, 2016 · b7d0fd6 · b7d0fd6
1 parent 3e40f80
commit b7d0fd6
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diff --git a/python/core/core.sip b/python/core/core.sip
@@ -148,6 +148,7 @@
 %Include qgsvectorlayerimport.sip
 %Include qgsvectorlayerjoinbuffer.sip
 %Include qgsvectorlayerundocommand.sip
+%Include qgsvectorlayerutils.sip
 %Include qgsvectorsimplifymethod.sip
 
 %Include qgscachedfeatureiterator.sip

diff --git a/python/core/qgsvectorlayerutils.sip b/python/core/qgsvectorlayerutils.sip
@@ -0,0 +1,22 @@
+
+/** \ingroup core
+ * \class QgsVectorLayerUtils
+ * \brief Contains utility methods for working with QgsVectorLayers.
+ *
+ * \note Added in version 3.0
+ */
+class QgsVectorLayerUtils
+{
+%TypeHeaderCode
+#include <qgsvectorlayerutils.h>
+%End
+  public:
+
+    /**
+     * Returns true if the specified value already exists within a field. This method can be used to test for uniqueness
+     * of values inside a layer's attributes. An optional list of ignored feature IDs can be provided, if so, any features
+     * with IDs within this list are ignored when testing for existance of the value.
+     */
+    static bool valueExists( const QgsVectorLayer* layer, int fieldIndex, const QVariant& value, const QgsFeatureIds& ignoreIds = QgsFeatureIds() );
+
+};
diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
@@ -230,6 +230,7 @@ SET(QGIS_CORE_SRCS
   qgsvectorlayerlabelprovider.cpp
   qgsvectorlayerrenderer.cpp
   qgsvectorlayerundocommand.cpp
+  qgsvectorlayerutils.cpp
   qgsvectorsimplifymethod.cpp
   qgsvirtuallayerdefinition.cpp
   qgsvirtuallayerdefinitionutils.cpp
@@ -722,6 +723,7 @@ SET(QGIS_CORE_HDRS
   qgsvectorlayerlabelprovider.h
   qgsvectorlayerrenderer.h
   qgsvectorlayerundocommand.h
+  qgsvectorlayerutils.h
   qgsvectorsimplifymethod.h
   qgsmapthemecollection.h
   qgsxmlutils.h

diff --git a/src/core/qgsvectorlayer.h b/src/core/qgsvectorlayer.h
@@ -403,6 +403,7 @@ struct CORE_EXPORT QgsVectorJoinInfo
  * Provider to display vector data in a GRASS GIS layer.
  *
  * TODO QGIS3: Remove virtual from non-inherited methods (like isModified)
+ * @see QgsVectorLayerUtils()
  */
 
 

diff --git a/src/core/qgsvectorlayerutils.cpp b/src/core/qgsvectorlayerutils.cpp
@@ -0,0 +1,51 @@
+/***************************************************************************
+  qgsvectorlayerutils.cpp
+  -----------------------
+  Date                 : October 2016
+  Copyright            : (C) 2016 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsvectorlayerutils.h"
+
+bool QgsVectorLayerUtils::valueExists( const QgsVectorLayer* layer, int fieldIndex, const QVariant& value, const QgsFeatureIds& ignoreIds )
+{
+  if ( !layer )
+    return false;
+
+  if ( fieldIndex < 0 || fieldIndex >= layer->fields().count() )
+    return false;
+
+  QString fieldName = layer->fields().at( fieldIndex ).name();
+
+  // build up an optimised feature request
+  QgsFeatureRequest request;
+  request.setSubsetOfAttributes( QgsAttributeList() );
+  request.setFlags( QgsFeatureRequest::NoGeometry );
+
+  // at most we need to check ignoreIds.size() + 1 - the feature not in ignoreIds is the one we're interested in
+  int limit = ignoreIds.size() + 1;
+  request.setLimit( limit );
+
+  request.setFilterExpression( QStringLiteral( "%1=%2" ).arg( QgsExpression::quotedColumnRef( fieldName ),
+                               QgsExpression::quotedValue( value ) ) );
+
+  QgsFeature feat;
+  QgsFeatureIterator it = layer->getFeatures( request );
+  while ( it.nextFeature( feat ) )
+  {
+    if ( ignoreIds.contains( feat.id() ) )
+      continue;
+
+    return true;
+  }
+
+  return false;
+}
diff --git a/src/core/qgsvectorlayerutils.h b/src/core/qgsvectorlayerutils.h
@@ -0,0 +1,41 @@
+/***************************************************************************
+  qgsvectorlayerutils.h
+  ---------------------
+  Date                 : October 2016
+  Copyright            : (C) 2016 by Nyall Dawson
+  Email                : nyall dot dawson at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSVECTORLAYERUTILS_H
+#define QGSVECTORLAYERUTILS_H
+
+#include "qgsvectorlayer.h"
+
+/** \ingroup core
+ * \class QgsVectorLayerUtils
+ * \brief Contains utility methods for working with QgsVectorLayers.
+ *
+ * \note Added in version 3.0
+ */
+
+class CORE_EXPORT QgsVectorLayerUtils
+{
+  public:
+
+    /**
+     * Returns true if the specified value already exists within a field. This method can be used to test for uniqueness
+     * of values inside a layer's attributes. An optional list of ignored feature IDs can be provided, if so, any features
+     * with IDs within this list are ignored when testing for existance of the value.
+     */
+    static bool valueExists( const QgsVectorLayer* layer, int fieldIndex, const QVariant& value, const QgsFeatureIds& ignoreIds = QgsFeatureIds() );
+
+};
+
+#endif // QGSVECTORLAYERUTILS_H
diff --git a/tests/src/python/CMakeLists.txt b/tests/src/python/CMakeLists.txt
@@ -111,6 +111,7 @@ ADD_PYTHON_TEST(PyQgsVectorColorRamp test_qgsvectorcolorramp.py)
 ADD_PYTHON_TEST(PyQgsVectorFileWriter test_qgsvectorfilewriter.py)
 ADD_PYTHON_TEST(PyQgsVectorLayer test_qgsvectorlayer.py)
 ADD_PYTHON_TEST(PyQgsVectorLayerEditBuffer test_qgsvectorlayereditbuffer.py)
+ADD_PYTHON_TEST(PyQgsVectorLayerUtils test_qgsvectorlayerutils.py)
 ADD_PYTHON_TEST(PyQgsZonalStatistics test_qgszonalstatistics.py)
 ADD_PYTHON_TEST(PyQgsMapLayerRegistry test_qgsmaplayerregistry.py)
 ADD_PYTHON_TEST(PyQgsVirtualLayerProvider test_provider_virtual.py)

diff --git a/tests/src/python/test_qgsvectorlayerutils.py b/tests/src/python/test_qgsvectorlayerutils.py
@@ -0,0 +1,88 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsVectorLayerUtils.
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = 'Nyall Dawson'
+__date__ = '25/10/2016'
+__copyright__ = 'Copyright 2016, The QGIS Project'
+# This will get replaced with a git SHA1 when you do a git archive
+__revision__ = '$Format:%H$'
+
+import qgis  # NOQA
+
+import os
+
+from qgis.PyQt.QtCore import QVariant
+
+from qgis.core import (QgsVectorLayer,
+                       QgsVectorLayerUtils,
+                       QgsField,
+                       QgsFields,
+                       QgsFeature
+                       )
+from qgis.testing import start_app, unittest
+from utilities import unitTestDataPath
+start_app()
+
+
+def createLayerWithOnePoint():
+    layer = QgsVectorLayer("Point?field=fldtxt:string&field=fldint:integer",
+                           "addfeat", "memory")
+    pr = layer.dataProvider()
+    f = QgsFeature()
+    f.setAttributes(["test", 123])
+    assert pr.addFeatures([f])
+    assert layer.pendingFeatureCount() == 1
+    return layer
+
+
+class TestQgsVectorLayerUtils(unittest.TestCase):
+
+    def test_value_exists(self):
+        layer = createLayerWithOnePoint()
+        # add some more features
+        f1 = QgsFeature(2)
+        f1.setAttributes(["test1", 124])
+        f2 = QgsFeature(3)
+        f2.setAttributes(["test2", 125])
+        f3 = QgsFeature(4)
+        f3.setAttributes(["test3", 126])
+        f4 = QgsFeature(5)
+        f4.setAttributes(["test4", 127])
+        layer.dataProvider().addFeatures([f1, f2, f3, f4])
+
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 0, 'test'))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 0, 'test1'))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 0, 'test4'))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 0, 'not present!'))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 1, 123))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 1, 124))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 1, 127))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 1, 99))
+
+        # no layer
+        self.assertFalse(QgsVectorLayerUtils.valueExists(None, 1, 123))
+        # bad field indexes
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, -1, 'test'))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 100, 'test'))
+
+        # with ignore list
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 0, 'test1', [3, 4, 5]))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 0, 'test1', [999999]))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 0, 'test1', [2]))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 0, 'test1', [99999, 2]))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 0, 'test1', [3, 4, 5, 2]))
+
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 1, 125, [2, 4, 5]))
+        self.assertTrue(QgsVectorLayerUtils.valueExists(layer, 1, 125, [999999]))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 1, 125, [3]))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 1, 125, [99999, 3]))
+        self.assertFalse(QgsVectorLayerUtils.valueExists(layer, 1, 125, [2, 4, 5, 3]))
+
+
+if __name__ == '__main__':
+    unittest.main()