Namespace-level access

Question

I have the following situation:

namespace MyFramework {
  class A {
    void some_function_I_want_B_to_use() {}
  };
  class B {
    B() {
      some_function_I_want_B_to_use() {}
    }
  };
}

where I want the some_function_I_want_B_to_use to not be visible outside of the MyFramework namespace, but I do want it to be visible to anyone inside of MyFramework (alternatively, visible to just class B is also ok). I've got a number of methods like this, is the only way to hide them from the public API of MyFramework to make all classes within MyFramework friends? I was also considering placing all "lower-level" classes inside of B, but I don't want to go down that route until I'm sure it would accomplish the ability to access all of A's methods from inside of B but not from outside of MyFramework.

To restate, I've got a framework that's all created within one namespace, and each class has methods that are useful to the general public using the framework. However, each class also has a few methods that complicate the public API but are needed for the framework to function properly.

Answer 1

I want the some_function_I_want_B_to_use to not be visible outside of the MyFramework namespace, but I do want it to be visible to anyone inside of MyFramework.

In summary, you want something similar to packages in Java.

Unfornately for you, that is not possible with namespaces. Every class included in a namespace is accessible from the outer of the namespace: namespaces are open.

The solution is usually to add another namespace for implementation details:

namespace MyFramework
{
    // Implementation details
    // Should not be used by the user
    namespace detail
    {
        class A
        {
            public:
                void func();
        };
    }

    class B
    {
        public:
            B()
            {
                A a;
                a.func();
            }
    };
}

Don't forget to add a comment stating the detail namespace is not to be used by user.