Re: forward declaration of an enumerated type

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 4 Jun 2007 15:38:07 -0400

Message-ID:

<f41pmv$6l9$1@news.datemas.de>

Dave Calkins wrote:

We routinely use forward declaration to avoid including header files
in header files. For example, if we have a class A which needs to
refer to class B we do the following in the header file:

--- A.h

class B;

class A { public: A(const B& rhs); ... }

---

This avoids needing to include B.h inside A.h and reduces unnecessary
include dependencies.

So, if some other header file defines an enumerated type, is there a
way to do something similar?

Not sure how you factor headers into that, but it should be possible.
For example, the program

    enum E;
    class A { public: A(E const& e); };
    enum E { one, two };
    A::A(E const& e) {}
    int main() {
        A a(one);
    }

compiles fine on VC++ 2005. I presume you have tried that. Didn't
it work? Visual C++ offers forward-declaration of enumerations as
an extension (as I understand it), it's not standard to forward-
declare an enumeration.

V
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