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78 lines
2.3 KiB
C++
78 lines
2.3 KiB
C++
/* ScummVM - Scumm Interpreter
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* Copyright (C) 2001 Ludvig Strigeus
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* Copyright (C) 2001-2005 The ScummVM project
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* $Header$
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*
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*/
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#ifndef COMMON_SINGLETON_H
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#define COMMON_SINGLETON_H
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namespace Common {
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/**
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* Generic template base class for implementing the singleton design pattern.
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*/
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template <class T>
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class Singleton
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{
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private:
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Singleton<T>(const Singleton<T>&);
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Singleton<T>& operator= (const Singleton<T>&);
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static T* _singleton;
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/**
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* The default object factory used by the template class Singleton.
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* By specialising this template function, one can make a singleton use a
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* custom object factory. For example, to support encapsulation, your
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* singleton class might be pure virtual (or "abstract" in Java terminology),
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* and you specialise makeInstance to return an instance of a subclass.
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*/
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//template <class T>
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static T* makeInstance() {
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return new T();
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}
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public:
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static T& instance() {
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// TODO: We aren't thread safe. For now we ignore it since the
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// only thing using this singleton template is the config manager,
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// and that is first instantiated long before any threads.
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// TODO: We don't leak, but the destruction order is nevertheless
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// semi-random. If we use multiple singletons, the destruction
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// order might become an issue. There are various approaches
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// to solve that problem, but for now this is sufficient
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if (!_singleton)
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_singleton = T::makeInstance();
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return *_singleton;
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}
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protected:
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Singleton<T>() { }
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virtual ~Singleton<T>() { }
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typedef T SingletonBaseType;
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};
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#define DECLARE_SINGLETON(T) template<> T* Common::Singleton<T>::_singleton=0
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} // End of namespace Common
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#endif
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