Support multi-field relations in createRelation().

Allow creating relations from a map of referenced->referencing fields.

Author: mohsenD98

src/core/utils/relationutils.cpp

@@ -45,19 +45,27 @@ QgsRelation RelationUtils::resolveReferencingRelation( QgsProject *project, QgsV
   return QgsRelation();
 }
 
-QgsRelation RelationUtils::createRelation( const QgsVectorLayer *referencedLayer, const QString &referencedFieldName, const QgsVectorLayer *referencingLayer, const QString &referencingFieldName )
+QgsRelation RelationUtils::createRelation( const QgsVectorLayer *referencedLayer, const QgsVectorLayer *referencingLayer, const QVariantMap &fieldPairs )
 {
-  if ( !referencedLayer || !referencingLayer )
+  if ( !referencedLayer || !referencingLayer || fieldPairs.isEmpty() )
     return QgsRelation();
 
-  const QString relationId = QStringLiteral( "%1_%2_%3_%4" ).arg( referencedLayer->id(), referencedFieldName, referencingLayer->id(), referencingFieldName );
+  QStringList fieldPairStrings;
+  for ( QVariantMap::const_iterator it = fieldPairs.constBegin(); it != fieldPairs.constEnd(); ++it )
+  {
+    fieldPairStrings.append( QStringLiteral( "%1_%2" ).arg( it.key(), it.value().toString() ) );
+  }
+  const QString relationId = QStringLiteral( "%1_%2_%3" ).arg( referencedLayer->id(), fieldPairStrings.join( "_" ), referencingLayer->id() );
 
   QgsRelation relation;
   relation.setId( relationId );
-  relation.setName( QStringLiteral( "%1 (%2) <-> %3 (%4)" ).arg( referencedLayer->name(), referencedFieldName, referencingLayer->name(), referencingFieldName ) );
+  relation.setName( QStringLiteral( "%1 (%2) <-> %3 (%4)" ).arg( referencedLayer->name(), fieldPairs.constBegin().key(), referencingLayer->name(), fieldPairs.constBegin().value().toString() ) );
   relation.setReferencedLayer( referencedLayer->id() );
   relation.setReferencingLayer( referencingLayer->id() );
-  relation.addFieldPair( referencingFieldName, referencedFieldName );
 
+  for ( QVariantMap::const_iterator it = fieldPairs.constBegin(); it != fieldPairs.constEnd(); ++it )
+  {
+    relation.addFieldPair( it.value().toString(), it.key() );
+  }
   return relation;
 }

src/core/utils/relationutils.h

@@ -37,13 +37,13 @@ class RelationUtils : public QObject
      * Note: Layers must be added to the project first
      *
      * \param referencedLayer The referenced (parent) layer
-     * \param referencedFieldName The field name in the referenced layer
      * \param referencingLayer The referencing (child) layer
-     * \param referencingFieldName The field name in the referencing layer that references the parent
+     * \param fieldPairs A map where keys are referenced field names and values are referencing field names
      * \returns A QgsRelation object
      */
-    Q_INVOKABLE QgsRelation createRelation( const QgsVectorLayer *referencedLayer, const QString &referencedFieldName,
-                                            const QgsVectorLayer *referencingLayer, const QString &referencingFieldName );
+    Q_INVOKABLE QgsRelation createRelation( const QgsVectorLayer *referencedLayer,
+                                            const QgsVectorLayer *referencingLayer,
+                                            const QVariantMap &fieldPairs );
 };
 
 #endif // RELATIONUTILS_H

test/qml/tst_relations.qml

@@ -42,7 +42,9 @@ TestCase {
     ProjectUtils.addMapLayer(qgisProject, referencingLayer);
 
     // 4) Create and register relation
-    let relation = RelationUtils.createRelation(referencedLayer, "district_uuid", referencingLayer, "parent_district_uuid");
+    let relation = RelationUtils.createRelation(referencedLayer, referencingLayer, {
+        "district_uuid": "parent_district_uuid"
+      });
     verify(relation.isValid, "Relation should be valid");
     let relationManager = qgisProject.relationManager;
     relationManager.addRelation(relation);