Singleton.h

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// Copyright 2002-2016 CEA LIST
// SPDX-FileCopyrightText: 2022 CEA LIST <gael.de-chalendar@cea.fr>
//
// SPDX-License-Identifier: MIT
 
#ifndef LIMA_MISC_SINGLETON_H
#define LIMA_MISC_SINGLETON_H
#include <memory>
 
namespace Lima
{
 
template<typename Object>
class Singleton
{
public:
  Singleton() = default;
  virtual ~Singleton() = default;
 
  static const Object& single();
  static const Object* psingle();
 
  static Object& changeable();
  static Object* pchangeable();
 
 
private:
  Singleton(const Singleton<Object>&) = default;
  Singleton& operator=(Singleton<Object>&) = default;
 
  static std::unique_ptr< Object > s_instance;
};
 
template<typename Object>
std::unique_ptr< Object > Singleton<Object>::s_instance(new Object());
 
template<typename Object>
const Object& Singleton<Object>::single()
{
  if (s_instance == nullptr)
  {
    s_instance=std::unique_ptr< Object >(new Object());
  }
  return *s_instance;
}
 
template<typename Object>
const Object* Singleton<Object>::psingle()
{
  if (s_instance==nullptr)
  {
    s_instance=std::unique_ptr< Object >(new Object());
  }
  return s_instance.get();
}
 
template<typename Object>
Object& Singleton<Object>::changeable()
{
  if (s_instance==nullptr)
  {
    s_instance=std::unique_ptr< Object >(new Object());
  }
  return *s_instance;
}
 
template<typename Object>
Object* Singleton<Object>::pchangeable()
{
  if (s_instance==nullptr)
  {
    s_instance=std::unique_ptr< Object >(new Object());
  }
  return s_instance.get();
}
 
} // Lima
 
#endif