Issue #15 Added CActiveObserver and CActiveMutator

These extend CPassiveObserver and CPassiveMutator with a one-to-many request/reply pattern.

src/blackmisc/sharedstate/activeobserver.h

@@ -0,0 +1,58 @@
+/* Copyright (C) 2017
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution. No part of swift project, including this file, may be copied, modified, propagated,
+ * or distributed except according to the terms contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_SHAREDSTATE_ACTIVEOBSERVER_H
+#define BLACKMISC_SHAREDSTATE_ACTIVEOBSERVER_H
+
+#include "blackmisc/sharedstate/passiveobserver.h"
+#include "blackmisc/promise.h"
+#include "blackmisc/variant.h"
+#include "blackmisc/blackmiscexport.h"
+#include <QObject>
+#include <QSharedPointer>
+
+namespace BlackMisc
+{
+    namespace SharedState
+    {
+        /*!
+         * Extends CPassiveObserver with the ability to send requests and receive replies.
+         */
+        class BLACKMISC_EXPORT CActiveObserver final : public CPassiveObserver
+        {
+            Q_OBJECT
+            friend QSharedPointer<CActiveObserver>;
+
+            template <typename T, typename F>
+            CActiveObserver(T *parent, F eventHandler) : CPassiveObserver(parent, eventHandler) {}
+
+        public:
+            //! Factory method.
+            template <typename T, typename F>
+            static auto create(T *parent, F eventHandler) { return QSharedPointer<CActiveObserver>::create(parent, eventHandler); }
+
+            //! Send a request and receive a synchronous reply.
+            CVariant request(const CVariant &param);
+
+            //! Send a request and receive an asynchronous reply.
+            //! The callback will not be called if the reply is received after the observer has been destroyed.
+            void requestAsync(const CVariant &param, std::function<void(const CVariant &)> callback);
+
+            //! Get a QWeakPointer pointing to this object.
+            QWeakPointer<const CActiveObserver> weakRef() const { return qSharedPointerCast<const CActiveObserver>(CPassiveObserver::weakRef()); }
+
+        signals:
+            //! Emitted by request and requestAsync.
+            void requestPosted(const CVariant &param, BlackMisc::CPromise<BlackMisc::CVariant> o_reply);
+        };
+    }
+}
+
+#endif