TITLE: privately scoped enums

(Newsgroups: comp.lang.c++.moderated)


PROBLEM: "Christopher S. Kush" <cskush@vnet.ibm.com>

class Gunk {

public:
  <blah blah blah>

private:
  enum StateFlag { hosed, jolly, pensive, irked };

  struct GorpRecord {
    StateFlag  sf;
  };
};

"(S) private member "Gunk::StateFlag" cannot be accessed."

I've tried making GorpRecord a class, I've tried friendship between Gunk
and GorpRecord in both directions.  I want an enum that only Gunk and
GorpRecord know about.  I don't want to make the enum public.


RESPONSE: stephen.clamage@eng.sun.com, 20 Aug 96

Declaring a member class to be a friend is a little tricky.
You can do it this way:

class Gunk {

public:
  <blah blah blah>

private:
  enum StateFlag { hosed, jolly, pensive, irked };

  struct GorpRecord;  // forward declare the member class
  friend GorpRecord;  // make the member class a friend
  struct GorpRecord { // define the member class
    StateFlag  sf;
  };
};

If you omit the forward declaration and just say
"friend struct GorpRecord", it would refer to some global
struct GorpRecord, not a member one.

There are other ways to get similar effects, but if you really
don't want ANY other class to know about the enum, this
solution will work.