Re: class does not want to get friends with another class

[David Hagood <david dot hagood at gmail dot com>]

On Thu, 2010-10-07 at 14:08 -0700, brac37 wrote:
> Hello,
> 
> I have some code that works when I make class classA public. But I only want
> class classA to be accessible by itself and class classB. So the problem is
> very concrete: make classB a friend of classA.
> 
> Here is the code that describes both classes.
> 
> 
> 
> template <class T, int C> class classA;
> 
> template <class T, int C, classA<T,C> &instanceA> class classB;
> 
> template <class T, int C> class classA
> {
> 
>   template <classA &instanceA> friend class classB;
I think your problem is that you are not fully specifying the template
parameters for class B, thus as far as class A is concerned, you are
speaking of some other class B.

I think you have to fully spec out class B here:

friend class classB<T,C,classA&>;

> 
> 
> private:
>   int for_use_by_classB;
> 
> };
> 
> template <class T, int C, classA<T,C> &instanceA> class classB
> {
> 
>   classB (int i) { instanceA.for_use_by_classB = i; }
> 
> };
> 
> // instantiation gives error
> // template class classA<char,128>;
>