C++ - Singleton

Singleton plays an important role in program architecturing for its global visibility. For instance, system parameters are usually structured as a singleton. What deserves to be noticed, a singleton can be realized in a variety of manners.

Taking C++ for instance, a typical singleton can be simply defined as

`singleton.h`

  #ifndef SINGLETON_H
  #define SINGLETON_H

  class Singleton
  {
  private:
      static Singleton *instance;
      Singleton() = default;
      Singleton(const Singleton &rhs) = delete;
      Singleton& operator=(const Singleton &rhs) = delete;
  public:
      static Singleton* get_instance();
  };

  #endif /* SINGLETON_H */

`singleton.cpp`

  #include "singleton.h"

  Singleton *Singleton::instance = nullptr;

  Singleton* Singleton::get_instance()
  {
      if (instance == nullptr)
          instance = new Singleton;
      return instance;
  }