[MeL] Mv Element::getNode() to TemplateElement.

This remove one dependencies on _nodes pointer C array.
If all dependencies are removed the memory for storing
the nodes can be in a std::array.

MeshLib/Elements/Element.cpp

@@ -82,21 +82,6 @@ std::optional<unsigned> Element::addNeighbor(Element* e)
     return std::optional<unsigned>();
 }
 
-const Node* Element::getNode(unsigned i) const
-{
-#ifndef NDEBUG
-    if (i < getNumberOfNodes())
-#endif
-    {
-        return _nodes[i];
-    }
-#ifndef NDEBUG
-    ERR("Error in MeshLib::Element::getNode() - Index {:d} in {:s}", i,
-        MeshElemType2String(getGeomType()));
-    return nullptr;
-#endif
-}
-
 void Element::setNode(unsigned idx, Node* node)
 {
 #ifndef NDEBUG

MeshLib/Elements/Element.h

@@ -54,7 +54,7 @@ public:
      * modifiable by the user) instance of class Node or a nullptr
      * @sa Element::getNodeIndex()
      */
-    const Node* getNode(unsigned i) const;
+    virtual const Node* getNode(unsigned i) const = 0;
 
     /**
      * (Re)Sets the node of the element.

MeshLib/Elements/TemplateElement-impl.h

@@ -100,4 +100,20 @@ bool TemplateElement<ELEMENT_RULE>::isEdge(unsigned idx1, unsigned idx2) const
     return false;
 }
 
+template <class ELEMENT_RULE>
+const Node* TemplateElement<ELEMENT_RULE>::getNode(unsigned i) const
+{
+#ifndef NDEBUG
+    if (i < getNumberOfNodes())
+#endif
+    {
+        return _nodes[i];
+    }
+#ifndef NDEBUG
+    ERR("Error in MeshLib::Element::getNode() - Index {:d} in {:s}", i,
+        MeshElemType2String(getGeomType()));
+    return nullptr;
+#endif
+}
+
 }  // namespace MeshLib

MeshLib/Elements/TemplateElement.h

@@ -188,6 +188,10 @@ public:
         return ELEMENT_RULE::computeVolume(this->_nodes);
     }
 
+    const Node* getNode(unsigned i) const override;
+    void setNode(unsigned idx, Node* node) override;
+    Node* const* getNodes() const override { return _nodes; }
+
     /// Return a specific edge node.
     inline Node* getEdgeNode(unsigned edge_id, unsigned node_id) const override
     {