chore: Add course material

397/Ex42/Subject.cpp

@@ -0,0 +1,12 @@
+
+
+#include "Subject.h"
+#include "Observer.h"
+
+void Subject::attach(Observer &obs) { myObservers.insert(&obs); }
+
+void Subject::notify() const {
+    for (ObsList::const_iterator iter = myObservers.begin(); iter != myObservers.end(); ++iter) {
+        (*iter)->update();
+    }
+}