From d99a1cac875820d1ab7abde8eee8a0f1b7336e32 Mon Sep 17 00:00:00 2001
From: Klaus Basan <klaus.basan@klausbasan.de>
Date: Mon, 12 Mar 2018 17:57:52 +0100
Subject: [PATCH] Ref T259, Ref T243 base class for providers/aware classes

* disable aware classes when provider is destroyed
* unified base class
---
 src/blackmisc/provider.h | 77 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 src/blackmisc/provider.h

diff --git a/src/blackmisc/provider.h b/src/blackmisc/provider.h
new file mode 100644
index 000000000..b559a9f93
--- /dev/null
+++ b/src/blackmisc/provider.h
@@ -0,0 +1,77 @@
+/* Copyright (C) 2018
+ * 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 and at http://www.swift-project.org/license.html. 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_PROVIDER_H
+#define BLACKMISC_PROVIDER_H
+
+#include "blackmisc/blackmiscexport.h"
+#include "blackmisc/connectionguard.h"
+#include <QObject>
+#include <QMetaObject>
+
+namespace BlackMisc
+{
+    //! Base class for providers
+    class IProvider
+    {
+    public:
+        //! Return as QObject
+        virtual QObject *asQObject() { return nullptr; }
+    };
+
+    //! Base class of provider aware classes
+    template <class PROVIDER> class BLACKMISC_EXPORT IProviderAware
+    {
+    protected:
+        //! Ctor
+        IProviderAware(PROVIDER *provider = nullptr) { this->setProvider(provider); }
+
+        //! Has provider?
+        bool hasProvider() const { return m_provider; }
+
+        //! Set the provider
+        //! \remark use individual names to disambiguate
+        void setProvider(PROVIDER *provider)
+        {
+            if (m_provider) { m_lastProviderConnections.disconnectAll(); }
+            m_provider = provider; // new provider
+            IProvider *iProvider = dynamic_cast<IProvider *>(provider);
+            if (iProvider && iProvider->asQObject())
+            {
+                QMetaObject::Connection con = QObject::connect(iProvider->asQObject(), &QObject::destroyed, [ = ](QObject * obj) { this->onProviderDestroyed(obj); });
+                m_lastProviderConnections.append(con);
+            }
+        }
+
+        //! Provider
+        PROVIDER *provider() { return m_provider; }
+
+        //! Const provider
+        const PROVIDER *provider() const { return m_provider; }
+
+    private:
+        CConnectionGuard m_lastProviderConnections; //!< provider signal connections
+        PROVIDER *m_provider = nullptr; //!< access to provider object
+
+        //! Provider was deleted
+        virtual void onProviderDestroyed(QObject *obj)
+        {
+            if (!m_provider) { return; } // already cleaned relationship
+            PROVIDER *provider = qobject_cast<PROVIDER *>(obj); // provider is implemented by a QObject
+            if (provider != m_provider) { return; } // not our business
+            m_provider = nullptr;
+        }
+    };
+} // namespace
+
+Q_DECLARE_INTERFACE(BlackMisc::IProvider, "org.swift-project.blackmisc.iprovider")
+
+#endif // guard