[FEATURE] Duplicate features including children (one level deep) when relation strength is competition - configuration for the relationsstrength in the relation GUI [needs-docs]

python/core/qgsrelation.sip

@@ -19,6 +19,13 @@ class QgsRelation
 %End
   public:
 
+    enum RelationStrength
+    {
+      Association,
+      Composition
+
+    };
+
 
     QgsRelation();
 %Docstring
@@ -53,6 +60,12 @@ class QgsRelation
  Set a name for this relation
 %End
 
+    void setStrength( const RelationStrength &strength );
+%Docstring
+ Set a strength for this relation
+.. versionadded:: 3.0
+%End
+
     void setReferencingLayer( const QString &id );
 %Docstring
  Set the referencing (child) layer id. This layer will be searched in the registry.
@@ -158,6 +171,15 @@ class QgsRelation
  :rtype: str
 %End
 
+    RelationStrength strength() const;
+%Docstring
+ Returns the relation strength as a string
+
+ :return: strength
+.. versionadded:: 3.0
+ :rtype: RelationStrength
+%End
+
     QString id() const;
 %Docstring
  A (project-wide) unique id for this relation

python/core/qgsvectorlayerutils.sip

@@ -22,6 +22,38 @@ class QgsVectorLayerUtils
 %End
   public:
 
+    class QgsDuplicateFeatureContext
+{
+%Docstring
+ Contains mainly the QMap with QgsVectorLayer and QgsFeatureIds do list all the duplicated features
+
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsvectorlayerutils.h"
+%End
+      public:
+
+        QgsDuplicateFeatureContext();
+
+        QList<QgsVectorLayer *> layers() const;
+%Docstring
+ Returns all the layers in the member QMap mDuplicatedFeatures
+.. versionadded:: 3.0
+ :rtype: list of QgsVectorLayer
+%End
+
+        QgsFeatureIds duplicatedFeatures( QgsVectorLayer *layer ) const;
+%Docstring
+ Returns the duplicated features in the given layer
+.. versionadded:: 3.0
+ :rtype: QgsFeatureIds
+%End
+
+
+    };
+
     static bool valueExists( const QgsVectorLayer *layer, int fieldIndex, const QVariant &value, const QgsFeatureIds &ignoreIds = QgsFeatureIds() );
 %Docstring
  Returns true if the specified value already exists within a field. This method can be used to test for uniqueness
@@ -62,8 +94,18 @@ class QgsVectorLayerUtils
  :rtype: QgsFeature
 %End
 
+    static QgsFeature duplicateFeature( QgsVectorLayer *layer, const QgsFeature &feature, QgsProject *project, int depth, QgsDuplicateFeatureContext &duplicateFeatureContext /Out/ );
+%Docstring
+ Duplicates a feature and it's children (one level deep). It calls CreateFeature, so
+ default values and constraints (e.g., unique constraints) will automatically be handled.
+ The duplicated feature will be automatically inserted into the layer.
+.. versionadded:: 3.0
+ :rtype: QgsFeature
+%End
+
 };
 
+
 /************************************************************************
  * This file has been generated automatically from                      *
  *                                                                      *

src/app/qgsdiscoverrelationsdlg.cpp

@@ -43,6 +43,17 @@ void QgsDiscoverRelationsDlg::addRelation( const QgsRelation &rel )
   mRelationsTable->setItem( row, 2, new QTableWidgetItem( rel.fieldPairs().at( 0 ).referencingField() ) );
   mRelationsTable->setItem( row, 3, new QTableWidgetItem( rel.referencedLayer()->name() ) );
   mRelationsTable->setItem( row, 4, new QTableWidgetItem( rel.fieldPairs().at( 0 ).referencedField() ) );
+  if ( rel.strength() == QgsRelation::RelationStrength::Composition )
+  {
+    mRelationsTable->setItem( row, 5, new QTableWidgetItem( QStringLiteral( "Composition" ) ) );
+  }
+  else
+  {
+    mRelationsTable->setItem( row, 5, new QTableWidgetItem( QStringLiteral( "Association" ) ) );
+  }
+
+  mRelationsTable->item( row, 5 )->setToolTip( QStringLiteral( "Composition (child features will be copied too) or Association" ) );
+
 }
 
 QList<QgsRelation> QgsDiscoverRelationsDlg::relations() const

src/app/qgsrelationadddlg.cpp

@@ -33,6 +33,10 @@ QgsRelationAddDlg::QgsRelationAddDlg( QWidget *parent )
   mCbxReferencedLayer->setFilters( QgsMapLayerProxyModel::VectorLayer );
   mCbxReferencedField->setLayer( mCbxReferencedLayer->currentLayer() );
 
+  mCbxRelationStrength->addItem( "Association", QVariant::fromValue( QgsRelation::RelationStrength::Association ) );
+  mCbxRelationStrength->addItem( "Composition", QVariant::fromValue( QgsRelation::RelationStrength::Composition ) );
+  mCbxRelationStrength->setToolTip( QStringLiteral( "Composition (child features will be copied too) or Association" ) );
+
   mTxtRelationId->setPlaceholderText( tr( "[Generated automatically]" ) );
   checkDefinitionValid();
 
@@ -74,6 +78,10 @@ QString QgsRelationAddDlg::relationName()
   return mTxtRelationName->text();
 }
 
+QgsRelation::RelationStrength QgsRelationAddDlg::relationStrength()
+{
+  return mCbxRelationStrength->currentData().value<QgsRelation::RelationStrength>();
+}
 
 void QgsRelationAddDlg::checkDefinitionValid()
 {

src/app/qgsrelationadddlg.h

@@ -18,6 +18,7 @@
 #include <QDialog>
 #include "ui_qgsrelationadddlgbase.h"
 #include "qgis_app.h"
+#include "qgsrelation.h"
 
 class QgsVectorLayer;
 
@@ -33,7 +34,7 @@ class APP_EXPORT QgsRelationAddDlg : public QDialog, private Ui::QgsRelationAddD
     QList< QPair< QString, QString > > references();
     QString relationId();
     QString relationName();
-
+    QgsRelation::RelationStrength relationStrength();
 
   private slots:
 

src/app/qgsrelationmanagerdialog.cpp

@@ -77,6 +77,19 @@ void QgsRelationManagerDialog::addRelation( const QgsRelation &rel )
   item = new QTableWidgetItem( rel.id() );
   item->setFlags( Qt::ItemIsEditable );
   mRelationsTable->setItem( row, 5, item );
+
+
+  if ( rel.strength() == QgsRelation::RelationStrength::Composition )
+  {
+    item = new QTableWidgetItem( QStringLiteral( "Composition" ) );
+  }
+  else
+  {
+    item = new QTableWidgetItem( QStringLiteral( "Association" ) );
+  }
+  item->setFlags( Qt::ItemIsEditable );
+  mRelationsTable->setItem( row, 6, item );
+
   mRelationsTable->setSortingEnabled( true );
 }
 
@@ -116,6 +129,7 @@ void QgsRelationManagerDialog::mBtnAddRelation_clicked()
     relation.setId( relationId );
     relation.addFieldPair( addDlg.references().at( 0 ).first, addDlg.references().at( 0 ).second );
     relation.setName( addDlg.relationName() );
+    relation.setStrength( addDlg.relationStrength() );
 
     addRelation( relation );
   }

src/core/qgsrelation.cpp

@@ -36,6 +36,7 @@ QgsRelation QgsRelation::createFromXml( const QDomNode &node )
   QString referencedLayerId = elem.attribute( QStringLiteral( "referencedLayer" ) );
   QString id = elem.attribute( QStringLiteral( "id" ) );
   QString name = elem.attribute( QStringLiteral( "name" ) );
+  QString strength = elem.attribute( QStringLiteral( "strength" ) );
 
   const QMap<QString, QgsMapLayer *> &mapLayers = QgsProject::instance()->mapLayers();
 
@@ -66,6 +67,14 @@ QgsRelation QgsRelation::createFromXml( const QDomNode &node )
   relation.mReferencedLayer = qobject_cast<QgsVectorLayer *>( referencedLayer );
   relation.mRelationId = id;
   relation.mRelationName = name;
+  if ( strength == "Composition" )
+  {
+    relation.mRelationStrength = RelationStrength::Composition;
+  }
+  else
+  {
+    relation.mRelationStrength = RelationStrength::Association;
+  }
 
   QDomNodeList references = elem.elementsByTagName( QStringLiteral( "fieldRef" ) );
   for ( int i = 0; i < references.size(); ++i )
@@ -90,6 +99,14 @@ void QgsRelation::writeXml( QDomNode &node, QDomDocument &doc ) const
   elem.setAttribute( QStringLiteral( "name" ), mRelationName );
   elem.setAttribute( QStringLiteral( "referencingLayer" ), mReferencingLayerId );
   elem.setAttribute( QStringLiteral( "referencedLayer" ), mReferencedLayerId );
+  if ( mRelationStrength == RelationStrength::Composition )
+  {
+    elem.setAttribute( QStringLiteral( "strength" ), QStringLiteral( "Composition" ) );
+  }
+  else
+  {
+    elem.setAttribute( QStringLiteral( "strength" ), QStringLiteral( "Association" ) );
+  }
 
   Q_FOREACH ( const FieldPair &fields, mFieldPairs )
   {
@@ -114,6 +131,12 @@ void QgsRelation::setName( const QString &name )
   mRelationName = name;
 }
 
+
+void QgsRelation::setStrength( const RelationStrength &strength )
+{
+  mRelationStrength = strength;
+}
+
 void QgsRelation::setReferencingLayer( const QString &id )
 {
   mReferencingLayerId = id;
@@ -206,6 +229,11 @@ QString QgsRelation::name() const
   return mRelationName;
 }
 
+QgsRelation::RelationStrength QgsRelation::strength() const
+{
+  return mRelationStrength;
+}
+
 QString QgsRelation::id() const
 {
   return mRelationId;

src/core/qgsrelation.h

@@ -48,6 +48,17 @@ class CORE_EXPORT QgsRelation
 
   public:
 
+    /**
+     * enum for the relation strength
+     * Association, Composition
+     */
+    enum RelationStrength
+    {
+      Association, //!< Loose relation, related elements are not part of the parent and a parent copy will not copy any children.
+      Composition  //!< Fix relation, related elements are part of the parent and a parent copy will copy any children or delete of parent will delete children
+
+    };
+
 #ifndef SIP_RUN
 
     /**
@@ -109,6 +120,12 @@ class CORE_EXPORT QgsRelation
      */
     void setName( const QString &name );
 
+    /**
+     * Set a strength for this relation
+     * \since QGIS 3.0
+     */
+    void setStrength( const RelationStrength &strength );
+
     /**
      * Set the referencing (child) layer id. This layer will be searched in the registry.
      */
@@ -214,6 +231,14 @@ class CORE_EXPORT QgsRelation
      */
     QString name() const;
 
+    /**
+     * Returns the relation strength as a string
+     *
+     * \returns strength
+     * \since QGIS 3.0
+     */
+    RelationStrength strength() const;
+
     /**
      * A (project-wide) unique id for this relation
      *
@@ -345,6 +370,8 @@ class CORE_EXPORT QgsRelation
     //! The parent layer
     QgsVectorLayer *mReferencedLayer = nullptr;
 
+    RelationStrength mRelationStrength;
+
     /**
      * A list of fields which define the relation.
      *  In most cases there will be only one value, but multiple values
@@ -357,5 +384,6 @@ class CORE_EXPORT QgsRelation
 
 // Register QgsRelation for usage with QVariant
 Q_DECLARE_METATYPE( QgsRelation )
+Q_DECLARE_METATYPE( QgsRelation::RelationStrength )
 
 #endif // QGSRELATION_H

src/core/qgsvectorlayerutils.cpp

@@ -16,6 +16,9 @@
 #include "qgsvectorlayerutils.h"
 #include "qgsvectordataprovider.h"
 #include <QRegularExpression>
+#include "qgsproject.h"
+#include "qgsrelationmanager.h"
+#include "qgslogger.h"
 
 bool QgsVectorLayerUtils::valueExists( const QgsVectorLayer *layer, int fieldIndex, const QVariant &value, const QgsFeatureIds &ignoreIds )
 {
@@ -320,3 +323,87 @@ QgsFeature QgsVectorLayerUtils::createFeature( QgsVectorLayer *layer, const QgsG
   return newFeature;
 }
 
+QgsFeature QgsVectorLayerUtils::duplicateFeature( QgsVectorLayer *layer, const QgsFeature &feature, QgsProject *project, int depth, QgsDuplicateFeatureContext &duplicateFeatureContext )
+{
+  if ( !layer )
+    return QgsFeature();
+
+  if ( !layer->isEditable() )
+    return QgsFeature();
+
+  //get context from layer
+  QgsExpressionContext context = layer->createExpressionContext();
+  context.setFeature( feature );
+
+  //create the attribute map
+  QgsAttributes srcAttr = feature.attributes();
+  QgsAttributeMap dstAttr;
+  for ( int src = 0; src < srcAttr.count(); ++src )
+  {
+    dstAttr[ src ] = srcAttr.at( src );
+  }
+
+  QgsFeature newFeature = createFeature( layer, feature.geometry(), dstAttr, &context );
+
+  const QList<QgsRelation> relations = project->relationManager()->referencedRelations( layer );
+
+  for ( const QgsRelation &relation : relations )
+  {
+    //check if composition (and not association)
+    if ( relation.strength() == QgsRelation::Composition && depth < 1 )
+    {
+      depth++;
+      //get features connected over this relation
+      QgsFeatureIterator relatedFeaturesIt = relation.getRelatedFeatures( feature );
+      QgsFeatureIds childFeatureIds;
+      QgsFeature childFeature;
+      while ( relatedFeaturesIt.nextFeature( childFeature ) )
+      {
+        //set childlayer editable
+        relation.referencingLayer()->startEditing();
+        //change the fk of the child to the id of the new parent
+        for ( const QgsRelation::FieldPair &fieldPair : relation.fieldPairs() )
+        {
+          childFeature.setAttribute( fieldPair.first, newFeature.attribute( fieldPair.second ) );
+        }
+        //call the function for the child
+        duplicateFeature( relation.referencingLayer(), childFeature, project, depth, duplicateFeatureContext );
+
+        //add the new feature id for feedback
+        childFeatureIds.insert( childFeature.id() );
+      }
+
+      //store for feedback
+      duplicateFeatureContext.setDuplicatedFeatures( relation.referencingLayer(), childFeatureIds );
+    }
+  }
+
+  layer->addFeature( newFeature );
+
+  return newFeature;
+}
+
+QList<QgsVectorLayer *> QgsVectorLayerUtils::QgsDuplicateFeatureContext::layers() const
+{
+  QList<QgsVectorLayer *> layers;
+  QMap<QgsVectorLayer *, QgsFeatureIds>::const_iterator i;
+  for ( i = mDuplicatedFeatures.begin(); i != mDuplicatedFeatures.end(); ++i )
+    layers.append( i.key() );
+  return layers;
+}
+
+QgsFeatureIds QgsVectorLayerUtils::QgsDuplicateFeatureContext::duplicatedFeatures( QgsVectorLayer *layer ) const
+{
+  return mDuplicatedFeatures[layer];
+}
+
+void QgsVectorLayerUtils::QgsDuplicateFeatureContext::setDuplicatedFeatures( QgsVectorLayer *layer, QgsFeatureIds ids )
+{
+  mDuplicatedFeatures.insert( layer, ids );
+}
+/*
+QMap<QgsVectorLayer *, QgsFeatureIds>  QgsVectorLayerUtils::QgsDuplicateFeatureContext::duplicateFeatureContext() const
+{
+  return mDuplicatedFeatures;
+}
+*/

src/core/qgsvectorlayerutils.h

@@ -32,6 +32,43 @@ class CORE_EXPORT QgsVectorLayerUtils
 {
   public:
 
+    /**
+     * \ingroup core
+     * \class QgsDuplicateFeatureContext
+     * \brief Contains mainly the QMap with QgsVectorLayer and QgsFeatureIds do list all the duplicated features
+     *
+     * \since QGIS 3.0
+     */
+    class QgsDuplicateFeatureContext
+    {
+      public:
+
+        QgsDuplicateFeatureContext() {}
+
+        /**
+         * Returns all the layers in the member QMap mDuplicatedFeatures
+         * \since QGIS 3.0
+         */
+        QList<QgsVectorLayer *> layers() const;
+
+        /**
+         * Returns the duplicated features in the given layer
+         * \since QGIS 3.0
+         */
+        QgsFeatureIds duplicatedFeatures( QgsVectorLayer *layer ) const;
+
+
+      private:
+        QMap<QgsVectorLayer *, QgsFeatureIds> mDuplicatedFeatures;
+        friend class QgsVectorLayerUtils;
+
+        /**
+         * To set an entry to the member QMap mDuplicatedFeatures
+         * \since QGIS 3.0
+         */
+        void setDuplicatedFeatures( QgsVectorLayer *layer, QgsFeatureIds ids );
+    };
+
     /**
      * 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
@@ -68,6 +105,15 @@ class CORE_EXPORT QgsVectorLayerUtils
                                      const QgsAttributeMap &attributes = QgsAttributeMap(),
                                      QgsExpressionContext *context = nullptr );
 
+    /**
+     * Duplicates a feature and it's children (one level deep). It calls CreateFeature, so
+     * default values and constraints (e.g., unique constraints) will automatically be handled.
+     * The duplicated feature will be automatically inserted into the layer.
+     * \since QGIS 3.0
+     */
+    static QgsFeature duplicateFeature( QgsVectorLayer *layer, const QgsFeature &feature, QgsProject *project, int depth, QgsDuplicateFeatureContext &duplicateFeatureContext SIP_OUT );
+
 };
 
+
 #endif // QGSVECTORLAYERUTILS_H

src/ui/qgsdiscoverrelationsdlgbase.ui

@@ -62,6 +62,11 @@
        <string>Referenced Field</string>
       </property>
      </column>
+     <column>
+      <property name="text">
+       <string>Strength</string>
+      </property>
+     </column>
     </widget>
    </item>
    <item>

src/ui/qgsrelationadddlgbase.ui

@@ -7,31 +7,60 @@
     <x>0</x>
     <y>0</y>
     <width>581</width>
-    <height>267</height>
+    <height>342</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string>Add Relation</string>
   </property>
   <layout class="QGridLayout" name="gridLayout">
-   <item row="1" column="0">
+   <item row="1" column="2">
+    <widget class="QgsMapLayerComboBox" name="mCbxReferencedLayer"/>
+   </item>
+   <item row="2" column="0" colspan="2">
+    <widget class="QLabel" name="label_4">
+     <property name="text">
+      <string>Referenced Field</string>
+     </property>
+    </widget>
+   </item>
+   <item row="4" column="2">
+    <widget class="QgsFieldComboBox" name="mCbxReferencingField"/>
+   </item>
+   <item row="2" column="2">
+    <widget class="QgsFieldComboBox" name="mCbxReferencedField"/>
+   </item>
+   <item row="3" column="0" colspan="2">
+    <widget class="QLabel" name="label">
+     <property name="text">
+      <string>Referencing Layer (Child)</string>
+     </property>
+    </widget>
+   </item>
+   <item row="3" column="2">
+    <widget class="QgsMapLayerComboBox" name="mCbxReferencingLayer"/>
+   </item>
+   <item row="0" column="0">
     <widget class="QLabel" name="label_7">
      <property name="text">
       <string>Name</string>
      </property>
     </widget>
    </item>
-   <item row="4" column="1" colspan="2">
+   <item row="0" column="2">
-    <widget class="QgsMapLayerComboBox" name="mCbxReferencingLayer"/>
+    <widget class="QLineEdit" name="mTxtRelationName"/>
    </item>
-   <item row="9" column="0">
+   <item row="1" column="0" colspan="2">
-    <widget class="QLabel" name="label_5">
+    <widget class="QLabel" name="label_3">
      <property name="text">
-      <string>Id</string>
+      <string>Referenced Layer (Parent)</string>
      </property>
     </widget>
    </item>
-   <item row="15" column="0" colspan="3">
+   <item row="5" column="2" rowspan="2">
+    <widget class="QLineEdit" name="mTxtRelationId"/>
+   </item>
+   <item row="8" column="2">
     <widget class="QDialogButtonBox" name="mButtonBox">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
@@ -41,48 +70,29 @@
      </property>
     </widget>
    </item>
-   <item row="4" column="0">
+   <item row="4" column="0" colspan="2">
-    <widget class="QLabel" name="label">
-     <property name="text">
-      <string>Referencing Layer (Child)</string>
-     </property>
-    </widget>
-   </item>
-   <item row="5" column="1" colspan="2">
-    <widget class="QgsFieldComboBox" name="mCbxReferencingField"/>
-   </item>
-   <item row="5" column="0">
     <widget class="QLabel" name="label_2">
      <property name="text">
       <string>Referencing Field</string>
      </property>
     </widget>
    </item>
-   <item row="2" column="0">
+   <item row="7" column="0" colspan="2">
-    <widget class="QLabel" name="label_3">
+    <widget class="QLabel" name="label_6">
      <property name="text">
-      <string>Referenced Layer (Parent)</string>
+      <string>Relationship Strength</string>
      </property>
     </widget>
    </item>
-   <item row="3" column="0">
+   <item row="5" column="0" rowspan="2" colspan="2">
-    <widget class="QLabel" name="label_4">
+    <widget class="QLabel" name="label_5">
      <property name="text">
-      <string>Referenced Field</string>
+      <string>Id</string>
      </property>
     </widget>
    </item>
-   <item row="3" column="1" colspan="2">
+   <item row="7" column="2">
-    <widget class="QgsFieldComboBox" name="mCbxReferencedField"/>
+    <widget class="QComboBox" name="mCbxRelationStrength"/>
-   </item>
-   <item row="9" column="1" colspan="2">
-    <widget class="QLineEdit" name="mTxtRelationId"/>
-   </item>
-   <item row="2" column="1" colspan="2">
-    <widget class="QgsMapLayerComboBox" name="mCbxReferencedLayer"/>
-   </item>
-   <item row="1" column="1" colspan="2">
-    <widget class="QLineEdit" name="mTxtRelationName"/>
    </item>
   </layout>
  </widget>

src/ui/qgsrelationmanagerdialogbase.ui

@@ -43,21 +43,26 @@
        <string>Referencing Field</string>
       </property>
      </column>
-     <column>
-      <property name="text">
-       <string>Referenced Layer</string>
-      </property>
-     </column>
      <column>
       <property name="text">
        <string>Referenced Field</string>
       </property>
      </column>
+     <column>
+      <property name="text">
+       <string>Referenced Layer</string>
+      </property>
+     </column>
      <column>
       <property name="text">
        <string>Id</string>
       </property>
      </column>
+     <column>
+      <property name="text">
+       <string>Strength</string>
+      </property>
+     </column>
     </widget>
    </item>
    <item>

tests/src/python/test_qgsvectorlayerutils.py

@@ -14,13 +14,16 @@ __revision__ = '$Format:%H$'
 
 import qgis  # NOQA
 
-from qgis.core import (QgsVectorLayer,
+from qgis.core import (QgsProject,
+                       QgsVectorLayer,
                        QgsVectorLayerUtils,
                        QgsFieldConstraints,
                        QgsFeature,
+                       QgsFeatureIterator,
                        QgsGeometry,
                        QgsPointXY,
                        QgsDefaultValue,
+                       QgsRelation,
                        NULL
                        )
 from qgis.testing import start_app, unittest
@@ -267,6 +270,159 @@ class TestQgsVectorLayerUtils(unittest.TestCase):
         f = QgsVectorLayerUtils.createFeature(layer, attributes={0: 'test_1', 1: 123})
         self.assertEqual(f.attributes(), ['test_4', 128, NULL])
 
+    def testDuplicateFeature(self):
+        """ test duplicating a feature """
+
+        project = QgsProject().instance()
+
+        # LAYERS
+        # - add first layer (parent)
+        layer1 = QgsVectorLayer("Point?field=fldtxt:string&field=pkid:integer",
+                                "parentlayer", "memory")
+        # > check first layer (parent)
+        self.assertTrue(layer1.isValid())
+        # -  set the value for the copy
+        layer1.setDefaultValueDefinition(1, QgsDefaultValue("rand(1000,2000)"))
+        # > check first layer (parent)
+        self.assertTrue(layer1.isValid())
+        # - add second layer (child)
+        layer2 = QgsVectorLayer("Point?field=fldtxt:string&field=id:integer&field=foreign_key:integer",
+                                "childlayer", "memory")
+        # > check second layer (child)
+        self.assertTrue(layer2.isValid())
+        # - add layers
+        project.addMapLayers([layer1, layer2])
+
+        # FEATURES
+        # - add 2 features on layer1 (parent)
+        l1f1orig = QgsFeature()
+        l1f1orig.setFields(layer1.fields())
+        l1f1orig.setAttributes(["F_l1f1", 100])
+        l1f2orig = QgsFeature()
+        l1f2orig.setFields(layer1.fields())
+        l1f2orig.setAttributes(["F_l1f2", 101])
+        # > check by adding features
+        self.assertTrue(layer1.dataProvider().addFeatures([l1f1orig, l1f2orig]))
+        # add 4 features on layer2 (child)
+        l2f1orig = QgsFeature()
+        l2f1orig.setFields(layer2.fields())
+        l2f1orig.setAttributes(["F_l2f1", 201, 100])
+        l2f2orig = QgsFeature()
+        l2f2orig.setFields(layer2.fields())
+        l2f2orig.setAttributes(["F_l2f2", 202, 100])
+        l2f3orig = QgsFeature()
+        l2f3orig.setFields(layer2.fields())
+        l2f3orig.setAttributes(["F_l2f3", 203, 100])
+        l2f4orig = QgsFeature()
+        l2f4orig.setFields(layer2.fields())
+        l2f4orig.setAttributes(["F_l2f4", 204, 101])
+        # > check by adding features
+        self.assertTrue(layer2.dataProvider().addFeatures([l2f1orig, l2f2orig, l2f3orig, l2f4orig]))
+
+        # RELATION
+        # - create the relationmanager
+        relMgr = project.relationManager()
+        # - create the relation
+        rel = QgsRelation()
+        rel.setId('rel1')
+        rel.setName('childrel')
+        rel.setReferencingLayer(layer2.id())
+        rel.setReferencedLayer(layer1.id())
+        rel.addFieldPair('foreign_key', 'pkid')
+        rel.setStrength(QgsRelation.Composition)
+        # > check relation
+        self.assertTrue(rel.isValid())
+        # - add relation
+        relMgr.addRelation(rel)
+        # > check if referencedLayer is layer1
+        self.assertEqual(rel.referencedLayer(), layer1)
+        # > check if referencingLayer is layer2
+        self.assertEqual(rel.referencingLayer(), layer2)
+        # > check if the layers are correct in relation when loading from relationManager
+        relations = project.relationManager().relations()
+        relation = relations[list(relations.keys())[0]]
+        # > check if referencedLayer is layer1
+        self.assertEqual(relation.referencedLayer(), layer1)
+        # > check if referencingLayer is layer2
+        self.assertEqual(relation.referencingLayer(), layer2)
+        # > check the relatedfeatures
+
+        '''
+        # testoutput 1
+        print( "\nAll Features and relations")
+        featit=layer1.getFeatures()
+        f=QgsFeature()
+        while featit.nextFeature(f):
+            print( f.attributes())
+            childFeature = QgsFeature()
+            relfeatit=rel.getRelatedFeatures(f)
+            while relfeatit.nextFeature(childFeature):
+                 print( childFeature.attributes() )
+        print( "\n--------------------------")
+
+        print( "\nFeatures on layer1")
+        for f in layer1.getFeatures():
+            print( f.attributes() )
+
+        print( "\nFeatures on layer2")
+        for f in layer2.getFeatures():
+            print( f.attributes() )
+        '''
+
+        # DUPLICATION
+        # - duplicate feature l1f1orig with children
+        layer1.startEditing()
+        results = QgsVectorLayerUtils.duplicateFeature(layer1, l1f1orig, project, 0)
+
+        # > check if name is name of duplicated (pk is different)
+        result_feature = results[0]
+        self.assertEqual(result_feature.attribute('fldtxt'), l1f1orig.attribute('fldtxt'))
+        # > check duplicated child layer
+        result_layer = results[1].layers()[0]
+        self.assertEqual(result_layer, layer2)
+        #  > check duplicated child features
+        self.assertTrue(results[1].duplicatedFeatures(result_layer))
+
+        '''
+        # testoutput 2
+        print( "\nFeatures on layer1 (after duplication)")
+        for f in layer1.getFeatures():
+            print( f.attributes() )
+
+        print( "\nFeatures on layer2 (after duplication)")
+        for f in layer2.getFeatures():
+            print( f.attributes() )
+            
+        print( "\nAll Features and relations")
+        featit=layer1.getFeatures()
+        f=QgsFeature()
+        while featit.nextFeature(f):
+            print( f.attributes())
+            childFeature = QgsFeature()
+            relfeatit=rel.getRelatedFeatures(f)
+            while relfeatit.nextFeature(childFeature):
+                 print( childFeature.attributes() )
+        '''
+
+        # > compare text of parent feature
+        self.assertEqual(result_feature.attribute('fldtxt'), l1f1orig.attribute('fldtxt'))
+
+        # - create copyValueList
+        childFeature = QgsFeature()
+        relfeatit = rel.getRelatedFeatures(result_feature)
+        copyValueList = []
+        while relfeatit.nextFeature(childFeature):
+            copyValueList.append(childFeature.attribute('fldtxt'))
+        # - create origValueList
+        childFeature = QgsFeature()
+        relfeatit = rel.getRelatedFeatures(l1f1orig)
+        origValueList = []
+        while relfeatit.nextFeature(childFeature):
+            origValueList.append(childFeature.attribute('fldtxt'))
+
+        # - check if the ids are still the same
+        self.assertEqual(copyValueList, origValueList)
+
 
 if __name__ == '__main__':
     unittest.main()