Update QgsDataDefined for expression contexts

Author: nyalldawson

python/core/qgsdatadefined.sip

@@ -120,14 +120,21 @@ class QgsDataDefined
      * @param layer vector layer
      * @returns true if expression was successfully prepared
      */
-    bool prepareExpression( QgsVectorLayer* layer );
+    bool prepareExpression( QgsVectorLayer* layer ) /Deprecated/;
 
     /** Prepares the expression using a fields collection
      * @param fields
      * @returns true if expression was successfully prepared
      * @note added in QGIS 2.9
      */
-    bool prepareExpression( const QgsFields &fields = QgsFields() );
+    bool prepareExpression( const QgsFields &fields ) /Deprecated/;
+
+    /** Prepares the expression using an expression context.
+     * @param context expression context
+     * @returns true if expression was successfully prepared
+     * @note added in QGIS 2.12
+     */
+    bool prepareExpression( const QgsExpressionContext &context = QgsExpressionContext() );
 
     /** Returns whether the data defined object's expression is prepared
      * @returns true if expression is prepared
@@ -139,13 +146,19 @@ class QgsDataDefined
     /** Returns the columns referenced by the QgsDataDefined
      * @param layer vector layer, used for preparing the expression if required
      */
-    QStringList referencedColumns( QgsVectorLayer* layer );
+    QStringList referencedColumns( QgsVectorLayer* layer ) /Deprecated/;
 
     /** Returns the columns referenced by the QgsDataDefined
      * @param fields vector layer, used for preparing the expression if required
      * @note added in QGIS 2.9
      */
-    QStringList referencedColumns( const QgsFields& fields = QgsFields() );
+    QStringList referencedColumns( const QgsFields& fields ) /Deprecated/;
+
+    /** Returns the columns referenced by the QgsDataDefined
+     * @param context expression context, used for preparing the expression if required
+     * @note added in QGIS 2.12
+     */
+    QStringList referencedColumns( const QgsExpressionContext& context = QgsExpressionContext() );
 
     /**
      * Get the field which this QgsDataDefined represents. Be aware that this may return

src/core/qgsdatadefined.cpp

@@ -115,6 +115,7 @@ void QgsDataDefined::setUseExpression( bool use )
 
   d.detach();
   d->useExpression = use;
+  d->expressionPrepared = false;
   d->exprRefColumns.clear();
 }
 
@@ -156,17 +157,22 @@ bool QgsDataDefined::prepareExpression( QgsVectorLayer* layer )
 {
   if ( layer )
   {
-    return prepareExpression( layer->fields() );
+    return prepareExpression( QgsExpressionContextUtils::createFeatureBasedContext( QgsFeature(), layer->fields() ) );
   }
   else
   {
-    //preparing expression without a layer set, so pass empty field list
-    QgsFields empty;
+    //preparing expression without a layer set, so pass empty context
+    QgsExpressionContext empty;
     return prepareExpression( empty );
   }
 }
 
 bool QgsDataDefined::prepareExpression( const QgsFields &fields )
+{
+  return prepareExpression( QgsExpressionContextUtils::createFeatureBasedContext( QgsFeature(), fields ) );
+}
+
+bool QgsDataDefined::prepareExpression( const QgsExpressionContext& context )
 {
   if ( !d->useExpression || d->expressionString.isEmpty() )
   {
@@ -194,7 +200,7 @@ bool QgsDataDefined::prepareExpression( const QgsFields &fields )
     }
   }
 
-  d->expression->prepare( fields );
+  d->expression->prepare( &context );
   d->exprRefColumns = d->expression->referencedColumns();
 
   if ( d->expression->hasEvalError() )
@@ -227,15 +233,21 @@ QStringList QgsDataDefined::referencedColumns( QgsVectorLayer* layer )
 {
   if ( layer )
   {
-    return referencedColumns( layer->fields() );
+    return referencedColumns( QgsExpressionContextUtils::createFeatureBasedContext( QgsFeature(), layer->fields() ) );
   }
   else
   {
-    return referencedColumns( );
+    QgsExpressionContext empty;
+    return referencedColumns( empty );
   }
 }
 
 QStringList QgsDataDefined::referencedColumns( const QgsFields &fields )
+{
+  return referencedColumns( QgsExpressionContextUtils::createFeatureBasedContext( QgsFeature(), fields ) );
+}
+
+QStringList QgsDataDefined::referencedColumns( const QgsExpressionContext& context )
 {
   if ( !d->exprRefColumns.isEmpty() )
   {
@@ -247,7 +259,7 @@ QStringList QgsDataDefined::referencedColumns( const QgsFields &fields )
   {
     if ( !d->expression || !d->expressionPrepared )
     {
-      prepareExpression( fields );
+      prepareExpression( context );
     }
   }
   else if ( !d->field.isEmpty() )

src/core/qgsdatadefined.h

@@ -21,6 +21,7 @@
 #include <QExplicitlySharedDataPointer>
 #include "qgis.h"
 #include "qgsfield.h"
+#include "qgsexpressioncontext.h"
 
 class QgsExpression;
 class QgsVectorLayer;
@@ -146,14 +147,21 @@ class CORE_EXPORT QgsDataDefined
      * @param layer vector layer
      * @returns true if expression was successfully prepared
      */
-    bool prepareExpression( QgsVectorLayer* layer );
+    Q_DECL_DEPRECATED bool prepareExpression( QgsVectorLayer* layer );
 
     /** Prepares the expression using a fields collection
      * @param fields
      * @returns true if expression was successfully prepared
      * @note added in QGIS 2.9
      */
-    bool prepareExpression( const QgsFields &fields = QgsFields() );
+    Q_DECL_DEPRECATED bool prepareExpression( const QgsFields &fields );
+
+    /** Prepares the expression using an expression context.
+     * @param context expression context
+     * @returns true if expression was successfully prepared
+     * @note added in QGIS 2.12
+     */
+    bool prepareExpression( const QgsExpressionContext &context = QgsExpressionContext() );
 
     /** Returns whether the data defined object's expression is prepared
      * @returns true if expression is prepared
@@ -165,13 +173,19 @@ class CORE_EXPORT QgsDataDefined
     /** Returns the columns referenced by the QgsDataDefined
      * @param layer vector layer, used for preparing the expression if required
      */
-    QStringList referencedColumns( QgsVectorLayer* layer );
+    Q_DECL_DEPRECATED QStringList referencedColumns( QgsVectorLayer* layer );
 
     /** Returns the columns referenced by the QgsDataDefined
      * @param fields vector layer, used for preparing the expression if required
      * @note added in QGIS 2.9
      */
-    QStringList referencedColumns( const QgsFields& fields = QgsFields() );
+    Q_DECL_DEPRECATED QStringList referencedColumns( const QgsFields& fields );
+
+    /** Returns the columns referenced by the QgsDataDefined
+     * @param context expression context, used for preparing the expression if required
+     * @note added in QGIS 2.12
+     */
+    QStringList referencedColumns( const QgsExpressionContext& context = QgsExpressionContext() );
 
     /**
      * Get the field which this QgsDataDefined represents. Be aware that this may return

tests/src/core/testqgsdatadefined.cpp

@@ -95,7 +95,7 @@ void TestQgsDataDefined::create()
 void TestQgsDataDefined::copy()
 {
   QgsDataDefined original( true, true, QString( "sqrt(2)" ), QString( "field" ) );
-  original.prepareExpression( NULL );
+  original.prepareExpression();
   QgsDataDefined copy( original );
   QVERIFY( copy == original );