singleton.H

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/*
  This file is part of Designar.
  Copyright (C) 2017 by Alejandro J. Mujica

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.

  Any user request of this software, write to 

  Alejandro Mujica

  aledrums@gmail.com
*/

# ifndef DSGSINGLETON_H
# define DSGSINGLETON_H

# include <memory>

namespace Designar
{

  template <typename T>
  class Singleton
  {
    static std::unique_ptr<Singleton<T>> instance;

  protected:
    Singleton()
    {
      // Empty
    }

    Singleton(const Singleton<T> &) = delete;

    Singleton & operator = (const Singleton<T> &) = delete;

  public:

    virtual ~Singleton()
    {
      // Empty
    }

    static T * get_ptr_instance()
    {
      if (instance.get() == nullptr)
    instance = std::unique_ptr<Singleton<T>>(new T());

      return static_cast<T *>(instance.get());
    }

    static T & get_instance()
    {
      return *get_ptr_instance();
    }
  };

  template <typename T>
  std::unique_ptr<Singleton<T>> Singleton<T>::instance =
    std::unique_ptr<Singleton<T>>(nullptr);

} // end namespace Designar

# endif // DSGSINGLETON_H