Fix grabbing of first QgsFeature; Cache QgsFeature being used to eval…

…; Handle layers with no objects
qgis · Oct 27, 2011 · 9b2bf0a · 9b2bf0a
1 parent 7940c39
commit 9b2bf0a
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Showing 2 changed files with 19 additions and 8 deletions.
diff --git a/src/gui/qgsexpressionbuilderwidget.cpp b/src/gui/qgsexpressionbuilderwidget.cpp
@@ -230,13 +230,24 @@ void QgsExpressionBuilderWidget::on_txtExpressionString_textChanged()
   // Maybe just calling exp.evaluate()?
   if ( mLayer )
   {
-    // TODO We should really cache the feature.
-    QgsFeature feature;
-    mLayer->featureAtId( 0 , feature );
-    QVariant value = exp.evaluate( &feature, mLayer->pendingFields() );
-
-    if ( !exp.hasEvalError() )
-      lblPreview->setText( value.toString() );
+    if ( !mFeature.isValid() )
+    {
+        mLayer->select( mLayer->pendingAllAttributesList() );
+        mLayer->nextFeature( mFeature );
+    }
+
+    if ( mFeature.isValid() )
+    {
+        QVariant value = exp.evaluate( &mFeature, mLayer->pendingFields() );
+        if ( !exp.hasEvalError() )
+          lblPreview->setText( value.toString() );
+    }
+    else
+    {
+        // The feautre is invaild because we don't have one but that doesn't mean user can't
+        // build a expression string.  They just get no preview.
+        lblPreview->setText("");
+    }
   }
 
   if ( exp.hasParserError() || exp.hasEvalError() )

diff --git a/src/gui/qgsexpressionbuilderwidget.h b/src/gui/qgsexpressionbuilderwidget.h
@@ -164,7 +164,7 @@ class GUI_EXPORT QgsExpressionBuilderWidget : public QWidget, private Ui::QgsExp
     QStandardItemModel *mModel;
     QgsExpressionItemSearchProxy *mProxyModel;
     QMap<QString, QgsExpressionItem*> mExpressionGroups;
-    QgsFeature* mFeature;
+    QgsFeature mFeature;
 };
 
 #endif // QGSEXPRESSIONBUILDER_H