Add QgsMemoryProviderUtils.createMemoryLayer for easy creation

of new memory layers from QgsFields/QgsCoordinateReferenceSystem/etc

Since memory provider cannot use QgsVectorLayerImport we need
another centeralized function for creating new memory layers
without the need to manually create the uri string.

python/CMakeLists.txt

@@ -107,6 +107,8 @@ INCLUDE_DIRECTORIES(
   ../src/core/layertree
   ../src/core/metadata
   ../src/core/processing
+  ../src/core/providers
+  ../src/core/providers/memory
   ../src/core/raster
   ../src/core/scalebar
   ../src/core/symbology-ng

python/core/core.sip

@@ -286,6 +286,8 @@
 %Include processing/qgsprocessingregistry.sip
 %Include processing/qgsprocessingutils.sip
 
+%Include providers/memory/qgsmemoryproviderutils.sip
+
 %Include raster/qgsbilinearrasterresampler.sip
 %Include raster/qgsbrightnesscontrastfilter.sip
 %Include raster/qgscliptominmaxenhancement.sip

python/core/providers/memory/qgsmemoryproviderutils.sip

@@ -9,6 +9,7 @@
 
 
 
+
 class QgsMemoryProviderUtils
 {
 %Docstring
@@ -21,6 +22,19 @@ class QgsMemoryProviderUtils
 %End
   public:
 
+    static QgsVectorLayer *createMemoryLayer( const QString &name,
+        const QgsFields &fields,
+        QgsWkbTypes::Type geometryType = QgsWkbTypes::NoGeometry,
+        const QgsCoordinateReferenceSystem &crs = QgsCoordinateReferenceSystem() ) /Factory/;
+%Docstring
+ Creates a new memory layer using the specified parameters. The caller takes responsibility
+ for deleting the newly created layer.
+ \param name layer name
+ \param fields fields for layer
+ \param geometryType optional layer geometry type
+ \param crs optional layer CRS for layers with geometry
+ :rtype: QgsVectorLayer
+%End
 };
 
 

src/app/CMakeLists.txt

@@ -500,6 +500,7 @@ INCLUDE_DIRECTORIES(
   ../core/dxf
   ../core/geometry
   ../core/layertree
+  ../core/providers/memory
   ../core/raster
   ../core/scalebar
   ../core/symbology-ng

src/core/CMakeLists.txt

@@ -94,6 +94,7 @@ SET(QGIS_CORE_SRCS
 
   providers/memory/qgsmemoryfeatureiterator.cpp
   providers/memory/qgsmemoryprovider.cpp
+  providers/memory/qgsmemoryproviderutils.cpp
 
   scalebar/qgsdoubleboxscalebarrenderer.cpp
   scalebar/qgsnumericscalebarrenderer.cpp
@@ -872,6 +873,7 @@ SET(QGIS_CORE_HDRS
   processing/qgsprocessingutils.h
 
   providers/memory/qgsmemoryfeatureiterator.h
+  providers/memory/qgsmemoryproviderutils.h
 
   raster/qgsbilinearrasterresampler.h
   raster/qgsbrightnesscontrastfilter.h

src/core/providers/memory/qgsmemoryproviderutils.cpp

@@ -16,3 +16,68 @@
  ***************************************************************************/
 
 #include "qgsmemoryproviderutils.h"
+#include "qgsfields.h"
+#include "qgsvectorlayer.h"
+
+QString memoryLayerFieldType( QVariant::Type type )
+{
+  switch ( type )
+  {
+    case QVariant::Int:
+      return QStringLiteral( "integer" );
+
+    case QVariant::LongLong:
+      return QStringLiteral( "long" );
+
+    case QVariant::Double:
+      return QStringLiteral( "double" );
+
+    case QVariant::String:
+      return QStringLiteral( "string" );
+
+    case QVariant::Date:
+      return QStringLiteral( "date" );
+
+    case QVariant::Time:
+      return QStringLiteral( "time" );
+
+    case QVariant::DateTime:
+      return QStringLiteral( "datetime" );
+
+    default:
+      return QStringLiteral( "string" );
+  }
+  return QStringLiteral( "string" ); // no warnings
+}
+
+QgsVectorLayer *QgsMemoryProviderUtils::createMemoryLayer( const QString &name, const QgsFields &fields, QgsWkbTypes::Type geometryType, const QgsCoordinateReferenceSystem &crs )
+{
+  QString geomType = QgsWkbTypes::displayString( geometryType );
+  if ( geomType.isNull() )
+    geomType = "none";
+
+  QString uri = geomType + '?';
+
+  bool first = true;
+  if ( crs.isValid() )
+  {
+    uri += QStringLiteral( "crs=" ) + crs.authid();
+    first = false;
+  }
+
+  QStringList fieldsStrings;
+  Q_FOREACH ( const QgsField &field, fields )
+  {
+    fieldsStrings << QStringLiteral( "field=%1:%2" ).arg( field.name(), memoryLayerFieldType( field.type() ) );
+  }
+
+  if ( !fieldsStrings.isEmpty() )
+  {
+    if ( !first )
+      uri += '&';
+    first = false;
+    uri += fieldsStrings.join( '&' );
+  }
+
+  return new QgsVectorLayer( uri, name, QStringLiteral( "memory" ) );
+}

src/core/providers/memory/qgsmemoryproviderutils.h

@@ -19,6 +19,13 @@
 #define QGSMEMORYPROVIDERUTILS_H
 
 #include "qgis_core.h"
+#include "qgis.h"
+#include "qgscoordinatereferencesystem.h"
+#include <QString>
+#include <QVariant>
+
+class QgsVectorLayer;
+class QgsFields;
 
 /**
  * \class QgsMemoryProviderUtils
@@ -31,6 +38,18 @@ class CORE_EXPORT QgsMemoryProviderUtils
 
   public:
 
+    /**
+     * Creates a new memory layer using the specified parameters. The caller takes responsibility
+     * for deleting the newly created layer.
+     * \param name layer name
+     * \param fields fields for layer
+     * \param geometryType optional layer geometry type
+     * \param crs optional layer CRS for layers with geometry
+     */
+    static QgsVectorLayer *createMemoryLayer( const QString &name,
+        const QgsFields &fields,
+        QgsWkbTypes::Type geometryType = QgsWkbTypes::NoGeometry,
+        const QgsCoordinateReferenceSystem &crs = QgsCoordinateReferenceSystem() ) SIP_FACTORY;
 };
 
 #endif // QGSMEMORYPROVIDERUTILS_H

src/gui/CMakeLists.txt

@@ -748,6 +748,7 @@ INCLUDE_DIRECTORIES(
   ../core/geometry
   ../core/layertree
   ../core/metadata
+  ../core/providers/memory
   ../core/raster
   ../core/scalebar
   ../core/symbology-ng

src/gui/qgsnewmemorylayerdialog.cpp

@@ -23,6 +23,7 @@
 #include "qgsvectordataprovider.h"
 #include "qgsvectorlayer.h"
 #include "qgssettings.h"
+#include "qgsmemoryproviderutils.h"
 
 #include <QPushButton>
 #include <QComboBox>
@@ -40,18 +41,8 @@ QgsVectorLayer *QgsNewMemoryLayerDialog::runAndCreateLayer( QWidget *parent, con
   }
 
   QgsWkbTypes::Type geometrytype = dialog.selectedType();
-
-  QString geomType = QgsWkbTypes::displayString( geometrytype );
-  if ( geomType.isNull() )
-    geomType = "none";
-
-  QString layerProperties = QStringLiteral( "%1?" ).arg( geomType );
-  if ( QgsWkbTypes::NoGeometry != geometrytype )
-    layerProperties.append( QStringLiteral( "crs=%1&" ).arg( dialog.crs().authid() ) );
-  layerProperties.append( QStringLiteral( "memoryid=%1" ).arg( QUuid::createUuid().toString() ) );
-
   QString name = dialog.layerName().isEmpty() ? tr( "New scratch layer" ) : dialog.layerName();
-  QgsVectorLayer *newLayer = new QgsVectorLayer( layerProperties, name, QStringLiteral( "memory" ) );
+  QgsVectorLayer *newLayer = QgsMemoryProviderUtils::createMemoryLayer( name, QgsFields(), geometrytype, dialog.crs() );
   return newLayer;
 }
 

tests/src/python/test_provider_memory.py

@@ -15,6 +15,7 @@
 
 from qgis.core import (
     QgsField,
+    QgsFields,
     QgsLayerDefinition,
     QgsPoint,
     QgsPathResolver,
@@ -23,7 +24,9 @@
     QgsFeature,
     QgsGeometry,
     QgsWkbTypes,
-    NULL
+    NULL,
+    QgsMemoryProviderUtils,
+    QgsCoordinateReferenceSystem
 )
 
 from qgis.testing import (
@@ -335,6 +338,58 @@ def testRenameAttributes(self):
         self.assertEqual(fet.fields()[1].name(), 'mapinfo_is_the_stone_age')
         self.assertEqual(fet.fields()[2].name(), 'super_size')
 
+    def testCreateMemoryLayer(self):
+        """
+        Test QgsMemoryProviderUtils.createMemoryLayer()
+        """
+
+        # no fields
+        layer = QgsMemoryProviderUtils.createMemoryLayer('my name', QgsFields())
+        self.assertTrue(layer.isValid())
+        self.assertEqual(layer.name(), 'my name')
+        self.assertTrue(layer.fields().isEmpty())
+
+        # geometry type
+        layer = QgsMemoryProviderUtils.createMemoryLayer('my name', QgsFields(), QgsWkbTypes.Point)
+        self.assertTrue(layer.isValid())
+        self.assertEqual(layer.wkbType(), QgsWkbTypes.Point)
+        layer = QgsMemoryProviderUtils.createMemoryLayer('my name', QgsFields(), QgsWkbTypes.PolygonZM)
+        self.assertTrue(layer.isValid())
+        self.assertEqual(layer.wkbType(), QgsWkbTypes.PolygonZM)
+
+        # crs
+        layer = QgsMemoryProviderUtils.createMemoryLayer('my name', QgsFields(), QgsWkbTypes.PolygonZM, QgsCoordinateReferenceSystem.fromEpsgId(3111))
+        self.assertTrue(layer.isValid())
+        self.assertEqual(layer.wkbType(), QgsWkbTypes.PolygonZM)
+        self.assertTrue(layer.crs().isValid())
+        self.assertEqual(layer.crs().authid(), 'EPSG:3111')
+
+        # fields
+        fields = QgsFields()
+        fields.append(QgsField("string", QVariant.String))
+        fields.append(QgsField("long", QVariant.LongLong))
+        fields.append(QgsField("double", QVariant.Double))
+        fields.append(QgsField("integer", QVariant.Int))
+        fields.append(QgsField("date", QVariant.Date))
+        fields.append(QgsField("datetime", QVariant.DateTime))
+        fields.append(QgsField("time", QVariant.Time))
+        layer = QgsMemoryProviderUtils.createMemoryLayer('my name', fields)
+        self.assertTrue(layer.isValid())
+        self.assertFalse(layer.fields().isEmpty())
+        self.assertEqual(len(layer.fields()), len(fields))
+        for i in range(len(fields)):
+            self.assertEqual(layer.fields()[i].name(), fields[i].name())
+            self.assertEqual(layer.fields()[i].type(), fields[i].type())
+
+        # unsupported field type
+        fields = QgsFields()
+        fields.append(QgsField("rect", QVariant.RectF))
+        layer = QgsMemoryProviderUtils.createMemoryLayer('my name', fields)
+        self.assertTrue(layer.isValid())
+        self.assertFalse(layer.fields().isEmpty())
+        self.assertEqual(layer.fields()[0].name(), 'rect')
+        self.assertEqual(layer.fields()[0].type(), QVariant.String) # should be mapped to string
+
 
 class TestPyQgsMemoryProviderIndexed(unittest.TestCase, ProviderTestCase):