Singleton.hpp

/* Copyright (c) 2013 David Sichau <mail"at"sichau"dot"eu>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 */

#ifndef UTILIB_SINGLETON_HPP_
#define UTILIB_SINGLETON_HPP_


#include <UtilLib/include/Exception.hpp>
namespace UtilLib {
template <class T>
class Singleton {
 public:
    // disallow creation, copying and assignment

    Singleton() = delete;

    Singleton(const Singleton& S) = delete;

    Singleton& operator=(const Singleton& S) = delete;

    static T& instance();

    ~Singleton();

 private:
    static void create();

    static T* pInstance_;

    static bool destroyed_;
};

template <class T>
T& Singleton<T>::instance() {
    if (!pInstance_) {
        if (destroyed_) {
            // dead reference
            throw Exception("The instance was already destroyed");
        } else {
            // initial creation
            create();
        }
    }
    return *pInstance_;
}

template <class T> Singleton<T>::~Singleton() {
    pInstance_ = 0;
    destroyed_ = true;
}

template <class T>
void Singleton<T>::create() {
    static T theInstance;
    pInstance_ = &theInstance;
}

template <class T>
T * Singleton<T>::pInstance_ = 0;
template <class T>
bool Singleton<T>::destroyed_ = false;
}

#endif /* UTILIB_SINGLETON_HPP_ */