source: XMLIO_V2/external/include/Poco/MetaObject.h @ 80

//
// MetaObject.h
//
// $Id: //poco/1.3/Foundation/include/Poco/MetaObject.h#1 $
//
// Library: Foundation
// Package: SharedLibrary
// Module:  ClassLoader
//
// Definition of the MetaObject class.
//
// Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_MetaObject_INCLUDED
#define Foundation_MetaObject_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include "Poco/SingletonHolder.h"
#include <set>


namespace Poco {


template <class B>
class AbstractMetaObject
        /// A MetaObject stores some information
        /// about a C++ class. The MetaObject class
        /// is used by the Manifest class.
        /// AbstractMetaObject is a common base class
        /// for all MetaObject in a rooted class hierarchy.
        /// A MetaObject can also be used as an object
        /// factory for its class.
{
public:
        AbstractMetaObject(const char* name): _name(name)
        {
        }

        virtual ~AbstractMetaObject()
        {
                for (typename ObjectSet::iterator it = _deleteSet.begin(); it != _deleteSet.end(); ++it)
                {
                        delete *it;
                }
        }

        const char* name() const
        {
                return _name;
        }

        virtual B* create() const = 0;
                /// Create a new instance of a class.
                /// Cannot be used for singletons.
                
        virtual B& instance() const = 0;
                /// Returns a reference to the only instance
                /// of the class. Used for singletons only.

        virtual bool canCreate() const = 0;
                /// Returns true iff the create method can be used
                /// to create instances of the class.
                /// Returns false if the class is a singleton.

        virtual void destroy(B* pObject) const
                /// If pObject was owned by meta object, the
                /// ownership of the deleted object is removed
                /// and the object is deleted.
        {
                typename ObjectSet::iterator it = _deleteSet.find(pObject);
                
                if (it != _deleteSet.end())
                {
                        _deleteSet.erase(pObject);
                        delete pObject;
                }
        }

        B* autoDelete(B* pObject) const
                /// Give ownership of pObject to the meta object.
                /// The meta object will delete all objects it owns
                /// when it is destroyed.
                ///
                /// Returns pObject.
        {
                if (this->canCreate()) // guard against singleton
                {
                        poco_check_ptr (pObject);
                        _deleteSet.insert(pObject);
                }
                else throw InvalidAccessException("Cannot take ownership of", this->name());

                return pObject;
        }

        virtual bool isAutoDelete(B* pObject) const
                /// Returns true if the object is owned
                /// by meta object.
                ///
                /// Overloaded in MetaSingleton - returns true
                /// if the class is a singleton.
        {
                return _deleteSet.find(pObject) != _deleteSet.end();
        }

private:
        AbstractMetaObject();
        AbstractMetaObject(const AbstractMetaObject&);
        AbstractMetaObject& operator = (const AbstractMetaObject&);

        typedef std::set<B*> ObjectSet;
        
        const char* _name;
        mutable ObjectSet _deleteSet;
};


template <class C, class B>
class MetaObject: public AbstractMetaObject<B>
        /// A MetaObject stores some information
        /// about a C++ class. The MetaObject class
        /// is used by the Manifest class.
        /// A MetaObject can also be used as an object
        /// factory for its class.
{
public:
        MetaObject(const char* name): AbstractMetaObject<B>(name)
        {
        }

        ~MetaObject()
        {
        }

        B* create() const
        {
                return new C;
        }
        
        B& instance() const
        {
                throw InvalidAccessException("Not a singleton. Use create() to create instances of", this->name());
        }
        
        bool canCreate() const
        {
                return true;
        }
};


template <class C, class B> 
class MetaSingleton: public AbstractMetaObject<B> 
        /// A SingletonMetaObject disables the create() method
        /// and instead offers an instance() method to access
        /// the single instance of its class. 
{ 
public: 
        MetaSingleton(const char* name): AbstractMetaObject<B>(name) 
        {
        }
        
        ~MetaSingleton() 
        {
        }
        
        B* create() const
        {
                throw InvalidAccessException("Cannot create instances of a singleton class. Use instance() to obtain a", this->name());
        }
        
        bool canCreate() const
        {
                return false;
        }

        B& instance() const
        {
                return *_object.get();
        }
      
        bool isAutoDelete(B* pObject) const
        {
                return true;
        }

private: 
        mutable SingletonHolder<C> _object; 
}; 


} // namespace Poco


#endif // Foundation_MetaObject_INCLUDED