Re: Dynamic enums

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From	Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups	comp.lang.java.help
Subject	Re: Dynamic enums
Date	Tue, 11 Oct 2011 22:05:40 -0400
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On 10/11/2011 9:34 PM, Linus Flustillbe wrote:
> Let's say I have an ENUM defined as
>
> public enum xxx {
>    A, B, C, D, E
> }
>
> Now here's my question.
> Let's say I have a table called foobar which has the following rows
>
> A  1
> B  2
> C  3
> D  4
> E  5
>
> My code is written and is working great.  The enum xxx is used as a
> lookup on the foobar table.  If I add a row to foobar like
>
> F  6
>
> I need to add another enum to the xxx enum and rebuild my project.
>
> So my question is, is there something like a dynamic enun:  by this
> could I call a method on the xxx enum like
>
> xxx.addnew("F") that would make F a valid enum of xxx and not have to
> rebuild my project?

     No.  The names of enum constants are compile-time artifacts,
just like the names of local variables.  At run-time, all such
things have disappeared (well, they may survive in ancillary debug
data, but the C language has no access to such things).

     Besides, what use could you make of such a dynamic enum, even
if you could create it?  If there's a `switch' with cases for
A,B,C,D,E, it won't magically acquire a new case for F.  If you've
got an array of the values A,B,C,D,E that you traverse from time to
time, the array won't magically lengthen and acquire an F-valued
element.  What do you expect to be able to do with F, given that the
code as written never mentions the identifier `F' at all?  (Worse,
what do you expect to do if the code *does* use `F', but in some
completely different context?  Does creating the dynamic enum `F'
cause a retroactive compilation failure?)

-- 
Eric Sosman
esosman@ieee-dot-org.invalid

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Thread

Dynamic enums Linus Flustillbe <admin@nacs.dyndns-office.com> - 2011-10-12 01:34 +0000
  Re: Dynamic enums Lew <lewbloch@gmail.com> - 2011-10-11 19:03 -0700
  Re: Dynamic enums Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-11 22:05 -0400
    Re: Dynamic enums Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-11 22:11 -0400
      Re: Dynamic enums Linus Flustillbe <admin@nacs.dyndns-office.com> - 2011-10-12 06:02 +0000
        Re: Dynamic enums markspace <-@.> - 2011-10-11 23:44 -0700
        Re: Dynamic enums Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-12 07:58 -0400
          Re: Dynamic enums markspace <-@.> - 2011-10-12 07:46 -0700
  Re: Dynamic enums markspace <-@.> - 2011-10-11 19:32 -0700
  Re: Dynamic enums Roedy Green <see_website@mindprod.com.invalid> - 2011-10-12 07:02 -0700

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