Re: Singleton class fails on reboot

From:

"mlimber" <mlimber@gmail.com>

Newsgroups:

comp.lang.c++,comp.os.ms-windows.programmer.win32

Date:

6 Jul 2006 05:44:54 -0700

Message-ID:

<1152189894.592630.254630@s26g2000cwa.googlegroups.com>

keepyourstupidspam@yahoo.co.uk wrote:

can someone explain to me how to implement this Just in time
singleton based on my current instance function.

Foo& Foo::Instance(void)
{
    if(_theInstance == 0)
        _theInstance = new Foo();
    return *_theInstance;
}

Well, we can't see the rest of your code, but here's a more complete
example:

template<class T>
class Singleton
{
public:
    static T& Instance();
private:
    // Disabled functions
    Singleton();
    Singleton( const Singleton& );
    Singleton& operator=( const Singleton& );
    Singleton* operator&();
    ~Singleton();
};

template<class T>
T& Singleton<T>::Instance()
{
    static T myObject;
    return myObject;
}

Which is used as a wrapper like this:

class A
{
public:
   void DoSomething();
   // ...

private:
   // Private constructor/destructor disallows creation
   // except by friends.
   friend class Singleton<A>;
   A();
   ~A();

   // Disabled functions for singleton usage
   A( const A& );
   A& operator=( const A& );
   A* operator&();
};

typedef Singleton<A> theA;

void Foo()
{
   theA::Instance().DoSomething();
}

See chapter 6 of _Modern C++ Design_ for more than you ever wanted to
know about templates in C++.

Cheers! --M