KillableSingleton.hpp

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/*
 
  This file is part of OpenFLUID software
  Copyright(c) 2021-2026, INRAE
 
 
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  it under the terms of the GNU General Public License as published by
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  GNU General Public License for more details.
 
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  along with OpenFLUID. If not, see <http://www.gnu.org/licenses/>.
 
 
 == Other Usage ==
 
  Other Usage means a use of OpenFLUID that is inconsistent with the GPL
  license, and requires a written agreement between You and INRA.
  Licensees for Other Usage of OpenFLUID may use this file in accordance
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*/
 
/**
  @file KillableSingleton.hpp
 
  @author Jean-Christophe FABRE <jean-christophe.fabre@inra.fr>
*/
 
 
#ifndef __OPENFLUID_UTILS_KILLABLESINGLETON_HPP__
#define __OPENFLUID_UTILS_KILLABLESINGLETON_HPP__
 
 
namespace openfluid { namespace utils {
 
/**
  Singleton template class implementing a killable singleton design.
  This implementation is not thread safe.
 
  @warning This template class does not work in a cross-dll context on Windows.
  Due to this restriction, it MUST NOT BE USED in the OpenFLUID framework.
 
  Example of use to design an Example class as a killable singleton
  @snippet misc/singleton.cpp killablesingleton
*/
template<typename T>
class KillableSingleton
{
 
  private:
 
    KillableSingleton<T>(T const&) = delete;
 
    void operator=(T const&) = delete;
 
 
  protected:
 
    static T* mp_Instance;
 
    KillableSingleton<T>() = default;
 
    ~KillableSingleton<T>()
    { }
 
 
  public:
 
    /**
      Returns a pointer to the singleton object.
      Instantiates the class if it not has not been instantiated before or it has been killed before.
      @return A pointer to the singleton object
    */
    static T* instance()
    {
      if (!mp_Instance)
      {
        mp_Instance = new T();
      }
 
      return mp_Instance;
    }
 
 
    // =====================================================================
    // =====================================================================
 
 
    /**
      Kills the singleton class
    */
    static void kill()
    {
      if (mp_Instance)
      {
        delete mp_Instance;
        mp_Instance = nullptr;
      }
    }
};
 
 
template <typename T>
T *KillableSingleton<T>::mp_Instance = nullptr;
 
 
} }  //namespaces
 
 
#endif /* __OPENFLUID_UTILS_KILLABLESINGLETON_HPP__ */