Make virtual fields updatable

Fix #11547
Fix #10994

Author: m-kuhn

python/core/qgsvectorlayer.sip

@@ -292,9 +292,11 @@ class QgsVectorLayer : QgsMapLayer
      * @param exp The expression which calculates the field
      * @param fld The field to calculate
      *
-     * @note added in 2.6
+     * @return The index of the new field
+     *
+     * @note added in 2.6, return value added in 2.9
      */
-    void addExpressionField( const QString& exp, const QgsField& fld );
+    int addExpressionField( const QString& exp, const QgsField& fld );
 
     /**
      * Remove an expression field
@@ -305,6 +307,28 @@ class QgsVectorLayer : QgsMapLayer
      */
     void removeExpressionField( int index );
 
+    /**
+     * Returns the expressoin used for a given expression field
+     *
+     * @param index An index of an epxression based (virtual) field
+     *
+     * @return The expression for the field at index
+     *
+     * @note added in 2.9
+     */
+    const QString expressionField( int index );
+
+    /**
+     * Changes the expression used to define an expression based (virtual) field
+     *
+     * @param index The index of the expression to change
+     *
+     * @param exp The new expression to set
+     *
+     * @note added in 2.9
+     */
+    void updateExpressionField( int index, const QString& exp );
+
     /** Get the label object associated with this layer */
     QgsLabel *label();
 

src/app/qgsfieldsproperties.cpp

@@ -20,6 +20,7 @@
 #include "qgsapplication.h"
 #include "qgsattributetypedialog.h"
 #include "qgsfieldcalculator.h"
+#include "qgsexpressionbuilderdialog.h"
 #include "qgsfieldsproperties.h"
 #include "qgslogger.h"
 #include "qgsmaplayerregistry.h"
@@ -249,6 +250,7 @@ void QgsFieldsProperties::setRow( int row, int idx, const QgsField& field )
     expressionWidget->setLayout( new QHBoxLayout );
     QToolButton* editExpressionButton = new QToolButton;
     editExpressionButton->setIcon( QgsApplication::getThemeIcon( "/mIconExpression.svg" ) );
+    connect( editExpressionButton, SIGNAL(clicked()), this, SLOT(updateExpression()) );
     expressionWidget->layout()->setContentsMargins( 0, 0, 0, 0 );
     expressionWidget->layout()->addWidget( editExpressionButton );
     expressionWidget->layout()->addWidget( new QLabel( mLayer->expressionField( idx ) ) );
@@ -657,6 +659,24 @@ void QgsFieldsProperties::attributesListCellChanged( int row, int column )
   }
 }
 
+void QgsFieldsProperties::updateExpression()
+{
+  QToolButton* btn = qobject_cast<QToolButton*>( sender() );
+  Q_ASSERT( btn );
+
+  int index = btn->property( "Index" ).toInt();
+
+  const QString exp = mLayer->expressionField( index );
+
+  QgsExpressionBuilderDialog dlg( mLayer, exp );
+
+  if ( dlg.exec() )
+  {
+    mLayer->updateExpressionField( index, dlg.expressionText() );
+    loadRows();
+  }
+}
+
 void QgsFieldsProperties::on_mCalculateFieldButton_clicked()
 {
   if ( !mLayer )

src/app/qgsfieldsproperties.h

@@ -183,6 +183,7 @@ class APP_EXPORT QgsFieldsProperties : public QWidget, private Ui_QgsFieldsPrope
 
     void attributesListCellChanged( int row, int column );
 
+    void updateExpression();
 
     /** editing of layer was toggled */
     void editingToggled();

src/core/qgsexpressionfieldbuffer.cpp

@@ -33,6 +33,11 @@ void QgsExpressionFieldBuffer::removeExpression( int index )
   mExpressions.removeAt( index );
 }
 
+void QgsExpressionFieldBuffer::updateExpression( int index, const QString& exp )
+{
+  mExpressions[index].expression = exp;
+}
+
 void QgsExpressionFieldBuffer::writeXml( QDomNode& layerNode, QDomDocument& document ) const
 {
   QDomElement expressionFieldsElem = document.createElement( "expressionfields" );

src/core/qgsexpressionfieldbuffer.h

@@ -58,6 +58,16 @@ class CORE_EXPORT QgsExpressionFieldBuffer
      */
     void removeExpression( int index );
 
+    /**
+     * Changes the expression at a given index
+     *
+     * @param index The index of the expression to change
+     * @param exp   The new expression to set
+     *
+     * @note added in 2.9
+     */
+    void updateExpression( int index, const QString& exp );
+
     /**
      * Saves expressions to xml under the layer node
      */

src/core/qgsvectorlayer.cpp

@@ -2843,12 +2843,13 @@ const QList< QgsVectorJoinInfo >& QgsVectorLayer::vectorJoins() const
   return mJoinBuffer->vectorJoins();
 }
 
-void QgsVectorLayer::addExpressionField( const QString& exp, const QgsField& fld )
+int QgsVectorLayer::addExpressionField( const QString& exp, const QgsField& fld )
 {
   mExpressionFieldBuffer->addExpression( exp, fld );
   updateFields();
   int idx = mUpdatedFields.indexFromName( fld.name() );
   emit attributeAdded( idx );
+  return idx;
 }
 
 void QgsVectorLayer::removeExpressionField( int index )
@@ -2865,6 +2866,12 @@ const QString QgsVectorLayer::expressionField( int index )
   return mExpressionFieldBuffer->expressions().value( oi ).expression;
 }
 
+void QgsVectorLayer::updateExpressionField(   int index, const QString& exp )
+{
+  int oi = mUpdatedFields.fieldOriginIndex( index );
+  mExpressionFieldBuffer->updateExpression( oi, exp );
+}
+
 void QgsVectorLayer::updateFields()
 {
   if ( !mDataProvider )

src/core/qgsvectorlayer.h

@@ -655,9 +655,11 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
      * @param exp The expression which calculates the field
      * @param fld The field to calculate
      *
-     * @note added in 2.6
+     * @return The index of the new field
+     *
+     * @note added in 2.6, return value added in 2.9
      */
-    void addExpressionField( const QString& exp, const QgsField& fld );
+    int addExpressionField( const QString& exp, const QgsField& fld );
 
     /**
      * Remove an expression field
@@ -668,8 +670,28 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
      */
     void removeExpressionField( int index );
 
+    /**
+     * Returns the expressoin used for a given expression field
+     *
+     * @param index An index of an epxression based (virtual) field
+     *
+     * @return The expression for the field at index
+     *
+     * @note added in 2.9
+     */
     const QString expressionField( int index );
 
+    /**
+     * Changes the expression used to define an expression based (virtual) field
+     *
+     * @param index The index of the expression to change
+     *
+     * @param exp The new expression to set
+     *
+     * @note added in 2.9
+     */
+    void updateExpressionField( int index, const QString& exp );
+
     /** Get the label object associated with this layer */
     QgsLabel *label();