Simple C++ Singleton Example

singleton.cpp

// C++ 11 way, thread-safe version, guaranteed to be destroyed.
// For further details, see §6.7 [stmt.dcl] p4 of C++ 11 standard

class Singleton
{
public:
    static Singleton& instance();
    
    Singleton(Singleton const&) = delete;        // Don't forget to disable copy
    void operator=(Singleton const&) = delete;   // Don't forget to disable copy
    
private:
    Singleton();       // forbid create instance outside
    ~Singleton();      // forbid to delete instance outside    
};

// Constructor & Dectructor
Singleton::Singleton() {
    
}

Singleton::~Singleton() {
    
}


// methods

Singleton& Singleton::instance() {
    // create instance by lazy initialization
    // guaranteed to be destroyed
    static Singleton instance;

    return instance;
}

singleton_basic.cpp

// C++ 98, non thread-safe version

class Singleton
{
public:
    static Singleton * instance();

private:
    Singleton();       // forbid create instance outside
    ~Singleton();      // forbid to delete instance outside

        
    Singleton(Singleton const&);        // Don't forget to disable copy
    void operator=(Singleton const&);   // Don't forget to disable copy
};

// Constructor & Dectructor
Singleton::Singleton() {
    
}

Singleton::~Singleton() {
    
}


// methods
Singleton * Singleton::instance() {
    // create new instance if null
    if(m_inst == NULL) {
        m_inst = new Singleton();
    }

    return m_inst;
}