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

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