[expressions] Allow conversion of features/geometries to bool

Where geometry = false if empty, feature = false if not valid. Allows expressions like "case when $geometry then ... else ..." and "case when get_feature(...) then ... else ... "
qgis · Nov 10, 2015 · 0853076 · 0853076
1 parent 719ff40
commit 0853076
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diff --git a/src/core/qgsexpression.cpp b/src/core/qgsexpression.cpp
@@ -371,6 +371,20 @@ static TVL getTVLValue( const QVariant& value, QgsExpression* parent )
   if ( value.isNull() )
     return Unknown;
 
+  //handle some special cases
+  if ( value.canConvert<QgsGeometry>() )
+  {
+    //geom is false if empty
+    QgsGeometry geom = value.value<QgsGeometry>();
+    return geom.isEmpty() ? False : True;
+  }
+  else if ( value.canConvert<QgsFeature>() )
+  {
+    //feat is false if non-valid
+    QgsFeature feat = value.value<QgsFeature>();
+    return feat.isValid() ? True : False;
+  }
+
   if ( value.type() == QVariant::Int )
     return value.toInt() != 0 ? True : False;
 

diff --git a/tests/src/core/testqgsexpression.cpp b/tests/src/core/testqgsexpression.cpp
@@ -630,6 +630,12 @@ class TestQgsExpression: public QObject
       QTest::newRow( "layer_property type" ) << QString( "layer_property('%1','type')" ).arg( mPointsLayer->name() ) << false << QVariant( "Vector" );
       QTest::newRow( "layer_property storage_type" ) << QString( "layer_property('%1','storage_type')" ).arg( mPointsLayer->name() ) << false << QVariant( "ESRI Shapefile" );
       QTest::newRow( "layer_property geometry_type" ) << QString( "layer_property('%1','geometry_type')" ).arg( mPointsLayer->name() ) << false << QVariant( "Point" );
+
+      //test conversions to bool
+      QTest::newRow( "feature to bool false" ) << QString( "case when get_feature('none','none',499) then true else false end" ) << false << QVariant( false );
+      QTest::newRow( "feature to bool true" ) << QString( "case when get_feature('test','col1',10) then true else false end" ) << false << QVariant( true );
+      QTest::newRow( "geometry to bool false" ) << QString( "case when geom_from_wkt('') then true else false end" ) << false << QVariant( false );
+      QTest::newRow( "geometry to bool true" ) << QString( "case when geom_from_wkt('Point(3 4)') then true else false end" ) << false << QVariant( true );
     }
 
     void run_evaluation_test( QgsExpression& exp, bool evalError, QVariant& result )