--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Messages/IObserver.h	Mon Jul 02 16:36:17 2018 +0200
@@ -0,0 +1,50 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2018 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+
+#pragma once
+
+#include "MessageBroker.h"
+
+namespace OrthancStone {
+
+  class IObservable;
+  class IMessage;
+
+  class IObserver : public boost::noncopyable
+  {
+    MessageBroker&                    broker_;
+
+  public:
+    IObserver(MessageBroker& broker)
+      : broker_(broker)
+    {
+      broker_.Register(*this);
+    }
+
+    virtual ~IObserver()
+    {
+      broker_.Unregister(*this);
+    }
+
+    virtual void HandleMessage(IObservable& from, const IMessage& message) = 0;
+  };
+
+}