ClickHouse/base/poco/Foundation/include/Poco/Observer.h

//
// Observer.h
//
// Library: Foundation
// Package: Notifications
// Module:  NotificationCenter
//
// Definition of the Observer class template.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier:	BSL-1.0
//


#ifndef Foundation_Observer_INCLUDED
#define Foundation_Observer_INCLUDED


#include "Poco/AbstractObserver.h"
#include "Poco/Foundation.h"
#include "Poco/Mutex.h"


namespace Poco
{


template <class C, class N>
class Observer : public AbstractObserver
/// This template class implements an adapter that sits between
/// a NotificationCenter and an object receiving notifications
/// from it. It is quite similar in concept to the
/// RunnableAdapter, but provides some NotificationCenter
/// specific additional methods.
/// See the NotificationCenter class for information on how
/// to use this template class.
///
/// Instead of the Observer class template, you might want to
/// use the NObserver class template, which uses an AutoPtr to
/// pass the Notification to the callback function, thus freeing
/// you from memory management issues.
{
public:
    typedef void (C::*Callback)(N *);

    Observer(C & object, Callback method) : _pObject(&object), _method(method) { }

    Observer(const Observer & observer) : AbstractObserver(observer), _pObject(observer._pObject), _method(observer._method) { }

    ~Observer() { }

    Observer & operator=(const Observer & observer)
    {
        if (&observer != this)
        {
            _pObject = observer._pObject;
            _method = observer._method;
        }
        return *this;
    }

    void notify(Notification * pNf) const
    {
        Poco::Mutex::ScopedLock lock(_mutex);

        if (_pObject)
        {
            N * pCastNf = dynamic_cast<N *>(pNf);
            if (pCastNf)
            {
                pCastNf->duplicate();
                (_pObject->*_method)(pCastNf);
            }
        }
    }

    bool equals(const AbstractObserver & abstractObserver) const
    {
        const Observer * pObs = dynamic_cast<const Observer *>(&abstractObserver);
        return pObs && pObs->_pObject == _pObject && pObs->_method == _method;
    }

    bool accepts(Notification * pNf) const { return dynamic_cast<N *>(pNf) != 0; }

    AbstractObserver * clone() const { return new Observer(*this); }

    void disable()
    {
        Poco::Mutex::ScopedLock lock(_mutex);

        _pObject = 0;
    }

private:
    Observer();

    C * _pObject;
    Callback _method;
    mutable Poco::Mutex _mutex;
};


} // namespace Poco


#endif // Foundation_Observer_INCLUDED