CPP

singleton c++

class S
{
    public:
        static S& getInstance()
        {
            static S    instance; // Guaranteed to be destroyed.
                                  // Instantiated on first use.
            return instance;
        }
    private:
        S() {}                    // Constructor? (the {} brackets) are needed here.

        // C++ 03
        // ========
        // Don't forget to declare these two. You want to make sure they
        // are unacceptable otherwise you may accidentally get copies of
        // your singleton appearing.
        S(S const&);              // Don't Implement
        void operator=(S const&); // Don't implement

        // C++ 11
        // =======
        // We can use the better technique of deleting the methods
        // we don't want.
    public:
        S(S const&)               = delete;
        void operator=(S const&)  = delete;

        // Note: Scott Meyers mentions in his Effective Modern
        //       C++ book, that deleted functions should generally
        //       be public as it results in better error messages
        //       due to the compilers behavior to check accessibility
        //       before deleted status
};

singleton c++

// NOTE in c++ a singleton is equivalent to just a namespace

class Singleton
{
public:
    // Prevents any type of copy or new instance
	Singleton(const Singleton&) = delete;
    void operator=(const Singleton&) = delete;
  
    static Singleton& Get()
    {
    	static Singleton instance;
    	return instance;
    }
  
    static int GetData() { return Get().someData}
private:
    Singleton() {}
	int someData = 1;
};