Re: Problem with Singleton template (2)

Hi best

Thanks very much for your reply. You were right, the compiler error
was just
my mis-typing. Sorry about that but I really appreciated your answer.
As you
predicted, my implementation failed because of the need to up-cast the
instance
pointer. So I am now trying to implement your suggestion. Here's an
outline of
my current code:

template <typename T> class Singleton
{
    public:
     static T* instance()
     {
         if (mp_instance == 0)
             mp_instance = new T; <<========= Line 48
         return mp_instance;
     }
    ...
    private:
     static T* mp_instance;
};

template <class T> class MyList
{
     friend class Singleton<MyList>;
....
}

class IntList : public MyList<int> { }; <<======= Line 26
typedef Singleton< IntList > theIntList;

main()
{
     theIntList* ptheIntList = theIntList::instance(); <<======= Line
31
     int length = ptheIntList->getListLength(0,0);
}

Now I get the following compiler errors:

line 26: error: "MyList<T>::MyList() [with T=int]" is inaccessible
detected during:
      implicit generation of "IntList::IntList()" at line 48 of
"Singleton.h"
      instantiation of "T *Singleton<T>::instance() [with T=IntList]"
at line 31
line 31: error: a value of type "IntList *" cannot be used to
initialize an entity of type "theIntList *"

Please can you suggest a fix for the errors? I can't see what is
wrong.

Do I need to make Singleton a friend of MyList as shown above?

Thanks again for your help.

David

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