Add node() function to OpticScenery.

Further work on NodeReference (not working yet :-( )

examples/pa_doublepass_graph.rs

-use opossum::nodes::{NodeDummy, NodeReference};
+use opossum::nodes::NodeDummy;
 use opossum::optic_node::OpticNode;
 use opossum::optic_scenery::OpticScenery;
 
@@ -13,11 +13,12 @@ fn main() {
     let n3 = scenery.add_node(OpticNode::new("Faraday", Box::new(NodeDummy)));
     let n4 = scenery.add_node(OpticNode::new("0° mirror", Box::new(NodeDummy)));
 
-    let mut node= OpticNode::new("Faraday", Box::new(NodeDummy));   
+    // let ref_node= NodeReference::new(scenery.node(n1));
+    // let n1r=scenery.add_node(OpticNode::new("ref", Box::new(ref_node)));
+
+    let mut node= OpticNode::new("Faraday", Box::new(NodeDummy));
     node.set_inverted(true);
-    let _ref_node= NodeReference::new(&node);
-    scenery.add_node(node);
-    //let n3i=scenery.add_node(OpticNode::new("ref", Box::new(ref_node)));
+    let n3i=scenery.add_node(node);
 
     let mut node= OpticNode::new("19mm amp", Box::new(NodeDummy));
     node.set_inverted(true);
@@ -30,8 +31,8 @@ fn main() {
     scenery.connect_nodes(n1, n2).unwrap();
     scenery.connect_nodes(n2, n3).unwrap();
     scenery.connect_nodes(n3, n4).unwrap();
-    // scenery.connect_nodes(n4, n3i).unwrap();
-    // scenery.connect_nodes(n3i, n2i).unwrap();
+    scenery.connect_nodes(n4, n3i).unwrap();
+    scenery.connect_nodes(n3i, n2i).unwrap();
     scenery.connect_nodes(n2i, n1i).unwrap();
 
     let path = "graph.dot";

src/nodes/node_reference.rs

@@ -12,7 +12,6 @@ impl<'a> NodeReference<'a> {
 }
 
 impl<'a> Optical for NodeReference<'a> {
-    /// Returns "dummy" as node type.
     fn node_type(&self) -> &str {
         "reference"
     }

src/optic_scenery.rs

 use crate::optic_node::OpticNode;
 use petgraph::algo::*;
-use petgraph::data::DataMap;
 use petgraph::prelude::{DiGraph, EdgeIndex, NodeIndex};
 
 #[derive(Debug, Clone)]
@@ -27,7 +26,17 @@ impl OpticScenery {
     pub fn add_node(&mut self, node: OpticNode) -> NodeIndex {
         self.g.add_node(node)
     }
-    /// Connect to (already existing) nodes denoted by the respective `NodeIndex`.
+    /// Get reference of [`OpticNode`].
+    ///
+    /// Get the reference of an previously added [`OpticNode`] denoted by a given `NodeIndex`. This function can be used as input while
+    /// constructing a `NodeReference`.
+    /// # Panics
+    ///
+    /// Panics if the given `NodeIndex` is not found in the graph.
+    pub fn node(&self, idx: NodeIndex) -> &OpticNode {
+        self.g.node_weight(idx).unwrap()
+    }
+    /// Connect (already existing) nodes denoted by the respective `NodeIndex`.
     ///
     /// Both node indices must exist. Otherwise an [`OpticSceneryError`] is returned. In addition, connections are
     /// rejected and an [`OpticSceneryError`] is returned, if the graph would form a cycle (loop in the graph).