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

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


#ifndef Foundation_NObserver_INCLUDED
#define Foundation_NObserver_INCLUDED


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


namespace Poco
{


template <class C, class N>
class NObserver : 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.
///
/// This class template is quite similar to the Observer class
/// template. The only difference is that the NObserver
/// expects the callback function to accept a const AutoPtr&
/// instead of a plain pointer as argument, thus simplifying memory
/// management.
{
public:
    typedef AutoPtr<N> NotificationPtr;
    typedef void (C::*Callback)(const NotificationPtr &);

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

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

    ~NObserver() { }

    NObserver & operator=(const NObserver & 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)
            {
                NotificationPtr ptr(pCastNf, true);
                (_pObject->*_method)(ptr);
            }
        }
    }

    bool equals(const AbstractObserver & abstractObserver) const
    {
        const NObserver * pObs = dynamic_cast<const NObserver *>(&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 NObserver(*this); }

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

        _pObject = 0;
    }

private:
    NObserver();

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


} // namespace Poco


#endif // Foundation_NObserver_INCLUDED