Friending an inner class to a templated class

[mrstephengross]

I'm making progress on mixing templates with friends (sounds like a
drinking game, huh?). Anyway, here's the situation. I've got an "Outer"
class with a private "Inner" class (sub-class, technically). I want to
declaring an unrelated "Thing" class to be a friend of the inner class.
However, since the inner class is private, the compiler complains.
Here's what the code looks like:
================================================== ==
template<typename Tclass Thing;

class Outer {
private:
class Inner {
public: friend class Thing<Outer::Inner>;
private: int x;
};
};

template<class Thing<Outer::Inner{ static void go() { Outer::Inner
i; } };
================================================== ====

So even though the friend statement should make the Inner class
accessible to class Thing, the compiler complains that Outer::Inner is
private, and thus inaccessible. Any ideas on how to make it work?

Thanks in advance,
--Steve (mr************@hotmail.com)

[Victor Bazarov]

mrstephengross wrote:

I'm making progress on mixing templates with friends (sounds like a
drinking game, huh?). Anyway, here's the situation. I've got an
"Outer" class with a private "Inner" class (sub-class, technically).
I want to declaring an unrelated "Thing" class to be a friend of the
inner class. However, since the inner class is private, the compiler
complains. Here's what the code looks like:
================================================== ==
template<typename Tclass Thing;

class Outer {
private:
class Inner {
public: friend class Thing<Outer::Inner>;
private: int x;
};
};

template<class Thing<Outer::Inner{ static void go() { Outer::Inner
i; } };
================================================== ====

So even though the friend statement should make the Inner class
accessible to class Thing, the compiler complains that Outer::Inner is
private, and thus inaccessible. Any ideas on how to make it work?

To let your 'Thing<Outer::Inner>' access 'Outer::Inner', it has to be
a friend of 'Outer', not of 'Outer::Inner'. You just gave your template
specialisation access to the 'x' variable. You didn't give access to
the 'Inner' type.

V
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