Optimised observer

libraries/observer.km3

@@ -0,0 +1,51 @@
+package app { 
+
+
+  class Subject {
+
+
+
+    attribute subjectState : OclAny;
+
+
+    reference views[*] : View oppositeOf subject;
+
+
+    query getState() : OclAny
+    pre: true
+    post: result = subjectState;
+
+    operation addView(v : View ) : void
+    pre: true
+    post: views->includes(v);
+
+    operation removeView(v : View ) : void
+    pre: true
+    post: views->excludes(v);
+
+  }
+
+
+
+
+  class View {
+
+
+    attribute viewState : OclAny; 
+
+    reference subject : Subject oppositeOf views;
+
+
+    operation refresh() : void
+    pre: true
+    post: viewState = subject.getState();
+
+  }
+
+
+
+
+
+}
+
+