Make Instrument2DItem::setDetectorGroup a template

GUI/Models/InstrumentItems.cpp

@@ -251,11 +251,6 @@ GroupItem* Instrument2DItem::detectorGroup()
     return item<GroupItem>(P_DETECTOR);
 }
 
-void Instrument2DItem::setDetectorGroup(const QString& modelType)
-{
-    setGroupProperty(P_DETECTOR, modelType);
-}
-
 void Instrument2DItem::clearMasks()
 {
     detectorItem()->clearMasks();

GUI/Models/InstrumentItems.h

@@ -101,7 +101,7 @@ public:
     DetectorItem* detectorItem() const;
     GroupItem* detectorGroup();
 
-    void setDetectorGroup(const QString& modelType);
+    template  <typename T> T* setDetectorGroup();
 
     void clearMasks() override;
     void importMasks(const MaskContainerItem* maskContainer) override;
@@ -177,4 +177,13 @@ T* InstrumentItem::setBackgroundType()
     return setGroupPropertyType<T>(P_BACKGROUND);
 }
 
+template <typename T>
+T* Instrument2DItem::setDetectorGroup()
+{
+    static_assert(std::is_base_of<DetectorItem,T>::value,
+                  "Class must be derived from DetectorItem");
+
+    return static_cast<T*>(setGroupProperty(P_DETECTOR, T::M_TYPE));
+}
+
 #endif // BORNAGAIN_GUI_MODELS_INSTRUMENTITEMS_H

GUI/Models/TransformFromDomain.cpp

@@ -298,12 +298,10 @@ void TransformFromDomain::setDetectorGeometry(Instrument2DItem* instrument_item,
                                               const IDetector& detector)
 {
     if (auto det = dynamic_cast<const SphericalDetector*>(&detector)) {
-        instrument_item->setDetectorGroup(SphericalDetectorItem::M_TYPE);
-        auto item = dynamic_cast<SphericalDetectorItem*>(instrument_item->detectorItem());
+        auto item = instrument_item->setDetectorGroup<SphericalDetectorItem>();
         setSphericalDetector(item, *det);
     } else if (auto det = dynamic_cast<const RectangularDetector*>(&detector)) {
-        instrument_item->setDetectorGroup(RectangularDetectorItem::M_TYPE);
-        auto item = dynamic_cast<RectangularDetectorItem*>(instrument_item->detectorItem());
+        auto item = instrument_item->setDetectorGroup<RectangularDetectorItem>();
         setRectangularDetector(item, *det);
     } else {
         throw Error(

Tests/UnitTests/GUI/TestLinkInstrument.cpp

@@ -37,7 +37,7 @@ TEST_F(TestLinkInstrument, test_canLinkToInstrument)
     EXPECT_EQ(manager.linkedRealDataItems(instrument), QList<RealDataItem*>() << realData);
 
     // changing detector type and checking that link remain
-    instrument->setDetectorGroup(RectangularDetectorItem::M_TYPE);
+    instrument->setDetectorGroup<RectangularDetectorItem>();
     EXPECT_EQ(manager.linkedRealDataItems(instrument), QList<RealDataItem*>() << realData);
 
     // changing detector binning and checking that link is destroyed