Issue #15 Classes for sharing a single value object,

built on top of the lower level API

src/blackmisc/sharedstate/scalarobserver.h

@@ -0,0 +1,78 @@
+/* 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_SCALAROBSERVER_H
+#define BLACKMISC_SHAREDSTATE_SCALAROBSERVER_H
+
+#include "blackmisc/sharedstate/activeobserver.h"
+#include "blackmisc/variant.h"
+#include "blackmisc/blackmiscexport.h"
+#include <QObject>
+#include <QMutex>
+
+namespace BlackMisc
+{
+    namespace SharedState
+    {
+        class IDataLink;
+
+        /*!
+         * Non-template base class for CScalarObserver.
+         */
+        class BLACKMISC_EXPORT CGenericScalarObserver : public QObject
+        {
+            Q_OBJECT
+
+        public:
+            //! Subscribe using the given transport mechanism.
+            void initialize(IDataLink *);
+
+        protected:
+            //! Constructor.
+            CGenericScalarObserver(QObject *parent) : QObject(parent) {}
+
+            //! Get scalar value as variant.
+            CVariant value() const;
+
+        private:
+            void reconstruct();
+            void handleEvent(const CVariant &param);
+            virtual void onGenericValueChanged(const CVariant &value) = 0;
+
+            QSharedPointer<CActiveObserver> m_observer = CActiveObserver::create(this, &CGenericScalarObserver::handleEvent);
+            mutable QMutex m_valueMutex;
+            CVariant m_value;
+        };
+
+        /*!
+         * Base class for an object that shares state with a corresponding CScalarMutator subclass object.
+         * \tparam T Datatype encapsulating the state to be shared.
+         */
+        template <typename T>
+        class CScalarObserver : public CGenericScalarObserver
+        {
+        protected:
+            //! Constructor.
+            CScalarObserver(QObject *parent) : CGenericScalarObserver(parent) {}
+
+        public:
+            //! Get scalar value.
+            T value() const { return CGenericScalarObserver::value().template to<T>(); }
+
+        private:
+            //! Called when the scalar value changes.
+            virtual void onValueChanged(const T &value) = 0;
+
+            virtual void onGenericValueChanged(const CVariant &value) override final { onValueChanged(value.to<T>()); }
+        };
+    }
+}
+
+#endif