How can the non-templated struct nested inside of a templated outer class access static members of the outer class?

Question

I swear I've searched all over the Internet and SO for this exact problem, but couldn't find any solutions.

Here's the setup:

template <typename T>
class Foo {
  static bool bar;

public:
  struct Baz {
    void quux() {
      // I want to access bar here
    }
  };
  // friend typename struct Foo<T>::Baz;
  // The above works, but I'm not sure if it's what I need?
};

Is what I'm trying to do possible?

Answer 1

The access is not a problem, just use Foo<T>::bar within Baz. I think that the bigger problem is that you need to allocate storage for Foo<T>::bar. This means that in your Foo.cpp file you'd have to actually instantiate all the templates you might think of using. For example:

template <typename T>
class Foo {
  static bool bar;
public:
  struct Baz {
    void quux() {
      // I want to access bar here
        Foo<T>::bar = true;
    }
  };
  static bool getBar() { return bar; }
};

// allocating storage for bars
template<>
bool Foo<int>::bar = false;
template<>
bool Foo<double>::bar = false;

int main() {
    Foo<int> fint;
    Foo<double> fouble;
    cout << Foo<int>::getBar() << " " << Foo<double>::getBar() << '\n';
    Foo<int>::Baz baz;
    baz.quux(); // alter int bar
    cout << Foo<int>::getBar() << " " << Foo<double>::getBar() << '\n';
}

Live demo