Add a method which builds an expression to test if a field is equal t…

…o a value
qgis · Jul 5, 2017 · 15546d8 · 15546d8
1 parent 8e43aca
commit 15546d8
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Showing 5 changed files with 34 additions and 27 deletions.
diff --git a/python/core/expression/qgsexpression.sip b/python/core/expression/qgsexpression.sip
@@ -495,6 +495,17 @@ return index of the function in Functions array
  :rtype: str
 %End
 
+    static QString createFieldEqualityExpression( const QString &fieldName, const QVariant &value );
+%Docstring
+ Create an expression allowing to evaluate if a field is equal to a
+  value. The value may be null.
+ \param fieldName the name of the field
+ \param value the value of the field
+ :return: the expression to evaluate field equality
+.. versionadded:: 3.0
+ :rtype: str
+%End
+
 };
 
 

diff --git a/src/core/expression/qgsexpression.cpp b/src/core/expression/qgsexpression.cpp
@@ -836,6 +836,18 @@ QString QgsExpression::formatPreviewString( const QVariant &value )
   }
 }
 
+QString QgsExpression::createFieldEqualityExpression( const QString &fieldName, const QVariant &value )
+{
+  QString expr;
+
+  if ( value.isNull() )
+    expr = QStringLiteral( "%1 IS NULL" ).arg( quotedColumnRef( fieldName ) );
+  else
+    expr = QStringLiteral( "%1 = %2" ).arg( quotedColumnRef( fieldName ), quotedValue( value ) );
+
+  return expr;
+}
+
 const QgsExpressionNode *QgsExpression::rootNode() const
 {
   return d->mRootNode;

diff --git a/src/core/expression/qgsexpression.h b/src/core/expression/qgsexpression.h
@@ -449,6 +449,15 @@ class CORE_EXPORT QgsExpression
      */
     static QString formatPreviewString( const QVariant &value );
 
+    /** Create an expression allowing to evaluate if a field is equal to a
+     *  value. The value may be null.
+     * \param fieldName the name of the field
+     * \param value the value of the field
+     * \returns the expression to evaluate field equality
+     * \since QGIS 3.0
+     */
+    static QString createFieldEqualityExpression( const QString &fieldName, const QVariant &value );
+
   private:
     void initGeomCalculator();
 

diff --git a/src/core/qgsrelation.cpp b/src/core/qgsrelation.cpp
@@ -170,18 +170,8 @@ QString QgsRelation::getRelatedFeaturesFilter( const QgsFeature &feature ) const
   {
     int referencingIdx = referencingLayer()->fields().indexFromName( fieldPair.referencingField() );
     QgsField referencingField = referencingLayer()->fields().at( referencingIdx );
-    const QString quotedColRef = QgsExpression::quotedColumnRef( fieldPair.referencingField() ) ;
-
     QVariant val( feature.attribute( fieldPair.referencedField() ) );
-
-    if ( val.isNull() )
-    {
-      conditions << QStringLiteral( "%1 IS NULL" ).arg( quotedColRef );
-    }
-    else
-    {
-      conditions << QStringLiteral( "%1 = %2" ).arg( quotedColRef, QgsExpression::quotedValue( val ) );
-    }
+    conditions << QgsExpression::createFieldEqualityExpression( fieldPair.referencingField(), val );
   }
 
   return conditions.join( QStringLiteral( " AND " ) );

diff --git a/src/gui/editorwidgets/qgsrelationreferencewidget.cpp b/src/gui/editorwidgets/qgsrelationreferencewidget.cpp
@@ -861,22 +861,7 @@ void QgsRelationReferenceWidget::filterChanged()
     if ( cb->currentIndex() != 0 )
     {
       const QString fieldName = cb->property( "Field" ).toString();
-
-      if ( cb->currentText() == nullValue.toString() )
-      {
-        filters << QStringLiteral( "\"%1\" IS NULL" ).arg( fieldName );
-      }
-      else
-      {
-        if ( mReferencedLayer->fields().field( fieldName ).type() == QVariant::String )
-        {
-          filters << QStringLiteral( "\"%1\" = '%2'" ).arg( fieldName, cb->currentText() );
-        }
-        else
-        {
-          filters << QStringLiteral( "\"%1\" = %2" ).arg( fieldName, cb->currentText() );
-        }
-      }
+      filters << QgsExpression::createFieldEqualityExpression( fieldName, cb->currentText() );
       attrs << mReferencedLayer->fields().lookupField( fieldName );
     }
   }