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Master Software Design Patterns and Architecture in C++

Singleton Pattern Implementation

Explore the Singleton pattern implementation in C++ by examining two practical examples. Understand the role of private constructors, static instance variables, and how to prevent copying. Learn Meyers' approach for thread-safe single instance creation and verify singleton behavior through output comparisons.

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Example one: simple implementation

Here’s an example of the singleton pattern implementation in C++.

C++
#include <iostream>
class MySingleton{
  private:
    static MySingleton* instance;
    MySingleton()= default;
    ~MySingleton()= default;
  public:
    MySingleton(const MySingleton&)= delete;
    MySingleton& operator=(const MySingleton&)= delete;
    static MySingleton* getInstance(){
      if ( !instance ){
        instance= new MySingleton();
      }
      return instance;
    }
};
MySingleton* MySingleton::instance= nullptr;
int main(){
  std::cout << '\n';
  std::cout << "MySingleton::getInstance(): "<< MySingleton::getInstance() << '\n';
  std::cout << "MySingleton::getInstance(): "<< MySingleton::getInstance() << '\n';
  std::cout << '\n';
}

Code explanation

  • Line 3 ...