Re: Singleton: type name is not allowed

From:

Victor Bazarov <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Wed, 25 Feb 2009 08:18:08 -0500

Message-ID:

<go3geh$p89$1@news.datemas.de>

srimks11@gmail.com wrote:

Dear All.

I am looking for small help on Singleton concept.

I had defined a singleton class as below -

---A.h---
class A
{
public:
    static A* Instance();
protected:
    A ();
private:
    static A* A_instance;
};

---A.cc----
A* A::A_instance = 0;

A* A::Instance()
    {
      if(A_instance == 0)
         {
          A_instance = new A;
         }
      return A_instance;
    }

A::A()
{
}
----

Now I wish to perform sole instance for below statement (i) using
above Singleton Instance() API call, originialy NonP is basically a
class.

NonP *nb = new NonP[524288];
-----(i)

I am aware about the syntax which should be somewhat as below -

NonP *nb = NonP[524288]::Instance();
--

But doing so, I get error message as -

"type name is not allowed"

Could anyone give the correct semantics for above (i)

Your problem is most likely due to the fact that arrays are not objects,
really. They are kind-of slap-together concept. So, you'd be much
better off *wrapping* your 'nb' array in a class. The simplest I can
think of is

     class NonP_Array {
         NonP data[524288];
         NonP_Array() {} // private default c-tor
         NonP_Array(NonP_Array const&) {} // private copy c-tor
         NonP_Array& operator=(NonP_Array const&) {} // private op=
     public:
         NonP& operator[](unsigned long i) { return data[i]; }
         static NonP_Array* Instance(); // do your singleton stuff
         ...
     };

Then do

     NonP_Array &np = *NonP_Array::Instance();

V
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